Synapse sends value_type field for .m.rule.is_user_mention, instead of value

[jplatte]

Matrix discussion (internal)

Currently, the push condition for the default rule .m.rule.is_user_mention looks like this in a (sliding) sync response:

{
    "kind": "event_property_contains",
    "key": "content.m\\.mentions.user_ids",
    "value_type": "user_id"
}

That last property should be "value": <actual user ID> instead.

[jplatte]

More context:

• sync response that contained this: here (internal)
• impact: This breaks ElementX parsing the push rules and thus degrades notifications for encrypted messages (not sure to what extent); we could implement a workaround to still parse the other push rules, or even interpret this unspecced thing

[clokep]

This should be being converted by the serialization code at

synapse/synapse/push/clientformat.py

Line 44 in 12e82fc

for type_key in ("pattern", "value"):