[buteo-sync-plugins-social] Remove unused dependency on contactcache

See merge request !97

common: add missing pkg-config dependency on libsocialcache

See merge request !96

The socialcache library is also used by the common library, so we need
to tell pkg-config about it.

[buteo-sync-plugins-social] Fix google calendar plugin adaptation to api changes. JB#53994

See merge request !95

[buteo-sync-plugins-social] Fix google calendar plugin adaptation to api changes. Contributes to JB#53994

Commit 1d80cc47 had quite a bunch of code churn and looks like this
change was missing.

Remove pragma and adjust the error api

See merge request !94

Api was changed to use enum type instead of vague int. Seems like this
was mixing up the enums.

Seems to compile without too and if the headers warn, then better to just
fix the problems there.

[buteo-sync-plugins-social] OneDrive backup uploads should use upload sessions. Fixes JB#53795

See merge request !93

OneDrive API has changed. The backup file url is now stored in the
"@microsoft.graph.downloadUrl" JSON value instead of
"@content.downloadUrl".

Since backup files may be large, they should be uploaded through
OneDrive's upload session feature, instead of the simple file upload
feature.

This involves calling createSessionUpload and then uploading the file
to the temporary URL provided by the server.

[buteo-sync-plugins-social] Adapt to changes in Buteo plugin API. JB#52916

See merge request !92

Out-of-process plugins are now built as .so Qt plugins, instead of as
executable binaries.

Also remove unnecessary OUT_OF_PROCESS_PLUGIN define as library is
always built as an out-of-process plugin.

[buteo-sync-plugins-social] Disable updating last modified time on event save. Contributes to JB#53475

See merge request !91

[buteo-sync-plugins-social] Disable updating last modified time on event save. Contributes to JB#53475

Previously, the backend would automatically update the last modified
time for an event when the event was saved.  Sync plugins (which
save updates to events due to server-side changes) should avoid this.

Recently, API was added to the backend calendar API to allow this
behaviour to be disabled by sync plugins.  This commit takes this
API into use, and removes the old work-arounds.

Jb53422

See merge request !90

The date of a Google birthday or event may be missing a 'year' value
even if it is otherwise valid. Also, a birthday may be just some
freeform text without a date. In these cases, ignore the value,
otherwise we will upload an invalid date on the next upsync and
overwrite the value on the server.

[buteo-sync-plugins-social] If Google contact sync fails, request full contact listing on next sync. JB#53422

This ensures the plugin cannot get into a loop where it continually
fails because of some sync conflict with the server, and thus can
never be synced. Doing a full contact listing on the next sync will
ensure we are up-to-date with the server's contacts.

If a retry fails, the next one will be a clean sync, and if that fails
there's no need to make another request after that.

[buteo-sync-plugins-social] Don't override user-selected calendar colors. JB#53286

See merge request !89

[buteo-sync-plugins-social] Sync the favorite status of Google contacts. JB#50799

See merge request !88

The favorite status is controlled by whether the contact is in the
"contactGroups/starred" contact group.

[buteo-sync-plugins-social] Update Contacts plugin to use Google People API. JB#50799

See merge request !86

The Google Contacts API is deprecated and the service will cease to
work in June 2021. Update the contacts plugin to use the newer People
API instead.

Main changes:
- Use JSON instead of XML to format request and response data.
- Make multi-part HTTP requests for batched upsync requests.
- Upsync avatar changes separately from other contact data as per the
People API requirements.
- Always save both the remote url and local file path for an avatar
instead of transforming the remote url to a local file after downloading.
- If a downloaded avatar's file extension does not match its meta type
(e.g. is png but has jpg extension) rename the file to match the type.

Handle Google downsynced all day event exceptions

See merge request !87

[buteo-sync-plugins-social] Handle Google downsynced all day event exceptions. Contributes to JB#52954

For Google calendar sync, if an exception for a recurring all day event
is downsynced from the server, the exception must be added to the rule
as a date, rather than a dateTime. Otherwise the exception fails to be
applied to the local calendar.

Combines various fixes to try to avoid sync errors blocking a sync from completing, and duplication of events

See merge request !84

During ghost event cleanup, any orphans that don't belong to any
notebook are deleted. This also purges them so they no longer exist in
the database after the sync.

The google sync plugin can be tricked into performing a "partial clean
sync" if both the syncToken and syncTime are invalid. This state can
occur, for example, if the account has never managed to complete a fully
successful sync.

The result of this state is that all events are considered as insertions
(as opposed to modifications), while at the same time the notebook isn't
recreated from scratch. As a result, duplicate entries are added to the
calendar on each sync.

This change fixes this by identifying the case where the syncToken and
syncTime are both invalid and ensuring the clean sync semantics are
applied throughout the sync (so everything is an insertion, but the
notebook is also recreated and so starts empty).

For accounts that have never experienced a successful sync, the last
sync time may return 0 with an invalid sync token. This will cause the
next sync to be clean, but with the requested minimum time set to 0
(i.e. "1970-01-01T00:00:00Z").

In practice, it never makes sense to sync back this far, so now the
start time is bounded below by a year prior to the current time.

Uses the volatile custom properties of KCalendarCore to store sync
errors for individual events, matching the approach used by the CalDav
plugin.

[buteo-sync-plugins-social] Add dummy parent if Google sends an exception without one. Contributes to JB#52608

If Google sends an exception event during a sync for which the parent
recurring event doesn't exist, this would previously cause the entire
sync to fail. This change instead creates a dummy parent event, matching
the exception, which the exeption is then dissociated from.

This allows the sync to succeed and the event to appear. This also
matches the behaviour of the caldav sync plugin.

If Google returns a 403 error it can mean modifying a non-authored
shared event, but it can also mean a usage limit has been reached. The
first is ignorable for the full sync, whereas the second should block
the full sync. They therefore need to be distinguished and handled
differently.

Delete events that return 404 errors are also handled differently. These
are ignored rather than causing the sync to fail.

When an account is initalised, a clean sync is initiated. However,
because the sync plugin version was left unset, the second was also
performed as a clean sync, even if the first was successful.

This change ensures the protocol version number gets stored correctly
after the first full sync in order to avoid this.

Combine common code and packages

See merge request !85