Clients will still only see this rule if the corresponding experimental
feature, `msc4028_push_encrypted_events`, is also enabled.

This aligns the implementation with MSC4028, specifically [this
section](https://github.com/matrix-org/matrix-spec-proposals/blob/giomfo/push_encrypted_events/proposals/4028-push-all-encrypted-events-except-for-muted-rooms.md#unstable-prefix).
See https://github.com/element-hq/synapse/issues/16846 for context.

Co-authored-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

During the migration the automated script to update the copyright
headers accidentally got rid of some of the existing copyright lines.
Reinstate them.

This unstable push rule is implemented behind an experimental
configuration flag.

* Updates the rule ID.
* Use `event_property_is` instead of `event_match`.

This updates the implementation of MSC3958 to match the latest
text from the MSC.

Also fix wrong rule names for `is_user_mention` and `is_room_mention`.

A dont_notify action is a no-op (and coalesce is undefined). These are
both considered no-ops by the spec, per MSC3987 and the predefined
push rules were updated to remove dont_notify from the list of actions.

This removes the experimental configuration option and
always escapes the push rule condition keys.

Also escapes any (experimental) push rule condition keys
in the base rules which contain dot in a field name.

This removes the configuration flag & updates the identifiers to
use the stable version.

Update intentional mentions (MSC3952) to depend on `exact_event_property_contains` (MSC3966). (#15051)

This replaces the specific `is_user_mention` push rule condition
used in MSC3952 with the generic `exact_event_property_contains`
push rule condition from MSC3966.

Internally the push rules module uses a `pattern_type` property for `event_match`
conditions (and `related_event_match`) to mark the condition as matching the
current user's Matrix ID or localpart.

This is leaky to the Client-Server API where a user can successfully set a condition
which provides `pattern_type` instead of `pattern` (note that there's no benefit to
doing this -- the user can just use their own Matrix ID or localpart instead). When
serializing back to the client the `pattern_type` property is converted into a proper
`pattern`.

The following changes are made to avoid this:

* Separate the `KnownCondition::EventMatch` enum value into `EventMatch`
  and `EventMatchType`, each with their own expected properties. (Note that a
  similar change is made for `RelatedEventMatch`.)
* Make it such that the `pattern_type` variants serialize to the same condition kind,
  but cannot be deserialized (since they're only provided by base rules).
* As a final tweak, convert `user_id` vs. `user_localpart` values into an enum.

This replaces the specific `is_room_mention` push rule condition
used in MSC3952 with the generic `exact_event_match` push rule
condition from MSC3758.

No functionality changes due to this.

This does nothing and I want to remove it from the MSC.

Co-authored-by: Brad Murray <brad@beeper.com>
Co-authored-by: Nick Barrett <nick@beeper.com>

Copy the suppress_edits push rule from Beeper to implement MSC3958.

https://github.com/beeper/synapse/blame/9415a1284b1bfb558bd66f28c24ca1611e6c6fa2/rust/src/push/base_rules.rs#L98-L114

* Correct the push rule IDs.
* Removes the sound tweak for room notifications.

MSC3952 defines push rules which searches for mentions in a list of
Matrix IDs in the event body, instead of searching the entire event
body for display name / local part.

This is implemented behind an experimental configuration flag and
does not yet implement the backwards compatibility pieces of the MSC.

* Support MSC1767's `content.body` behaviour in push rules

* Add the base rules from MSC3933

* Changelog entry

* Flip condition around for finding `m.markup`

* Remove forgotten import

MSC3772 has been abandoned.

Switches to the stable identifier for MSC3786 and enables it
by default.

This disables pushes of m.room.server_acl events.