Declare support for Matrix 1.3

[matrixbot]

This issue was originally created by @S7evinK at matrix-org/dendrite#3219.

Complete changelog v1.3

Client-Server API

Backwards Compatible Changes

• Make from optional on GET /_matrix/client/v3/messages to allow requesting events from the start or end of the room history, as per MSC3567.
  • While from is optional, it is not spec compliant
• Add refresh tokens, per MSC2918.
• Describe a structured system for event relationships, as per MSC2674.
• Describe how relationships between events can be "aggregated", as per MSC2675 and MSC3666.
• Add support for a new knock_restricted join rule in supported room versions, as per MSC3787.

Spec Clarifications

• Clarify that the url field in m.room.avatar events is not required. (#987)
• Clarify that the type in user-interactive authentication can be omitted. (#989)
  • Not optional in Dendrite
• Correct the default value for invite where it is not specified in an m.room.power_levels event. (#1021)
  • See Default PowerLevelContent.Invite to 0 per matrix spec matrix-org/gomatrixserverlib#416

Server-Server API

Backwards Compatible Changes

• Add a destination property to the Authorization header, as per MSC3383.

Spec Clarifications
(NOTE: Non-actionable things removed)

• Remove largely unused origin field from PDUs. (#998)
• Clarify the format for the Authorization header. (#1038, #1067)

Application Service API

Backwards Compatible Changes

• Add timestamp massaging as per MSC3316.

Room Versions

Backwards Compatible Changes

• Add room version 10 as per MSC3604.
• Enforce integer power levels in room version 10 as per MSC3667.
• Add a knock_restricted join rule supported by room version 10 as per MSC3787.

Spec Clarifications
(NOTE: Non-actionable things removed)

• For all room versions: Add m.federate to the authorization rules, as originally intended. (#1103)