Refactor PDU definitions to reduce duplication (#2070)

First of all, all PDU definitions were based on the v1 PDU definition with a few fields overwritten to change the format with needed.
While that works when rendering the spec, this is semantically incorrect because it means that the objects must match both schemas, which is impossible.

So now we make a base with only the common fields, and we add the others as needed by the room version.
Note that there is no more "unsigned PDU" definition since it is not used directly, and hashes and signatures are the same across all versions.

Signed-off-by: Kévin Commaille <zecakeh@tedomum.fr>

data/api/server-server/definitions/components/pdu_base.yaml

@@ -0,0 +1,86 @@
+# Copyright 2018 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+type: object
+description: Common fields for all PDU versions
+properties:
+  room_id:
+    type: string
+    description: Room identifier.
+    example: "!abc123:matrix.org"
+  sender:
+    type: string
+    description: The ID of the user sending the event.
+    example: "@someone:matrix.org"
+  origin_server_ts:
+    type: integer
+    format: int64
+    description: Timestamp in milliseconds on origin homeserver when this event was created.
+    example: 1234567890
+  type:
+    type: string
+    description: Event type
+    example: "m.room.message"
+  state_key:
+    type: string
+    description: |-
+      If this key is present, the event is a state event, and it will replace previous events
+      with the same `type` and `state_key` in the room state.
+    example: "my_key"
+  content:
+    type: object
+    description: The content of the event.
+    example: {"key": "value"}
+  depth:
+    type: integer
+    description: |-
+      The maximum depth of the `prev_events`, plus one. Must be less than the
+      maximum value for an integer (2^63 - 1). If the room's depth is already at
+      the limit, the depth must be set to the limit.
+    example: 12
+  hashes:
+    $ref: "event_hash.yaml"
+  signatures:
+    type: object
+    description: |-
+      Signatures for the PDU, following the algorithm specified in [Signing Events](/server-server-api/#signing-events).
+    example: {
+      "example.com": {
+        "ed25519:key_version:": "86BytesOfSignatureOfTheRedactedEvent"
+      }
+    }
+    additionalProperties:
+      type: object
+      title: Server Signatures
+      additionalProperties:
+        type: string
+  unsigned:
+    type: object
+    title: UnsignedData
+    description: |-
+      Additional data added by the origin server but not covered by the `signatures`.
+    example: {"key": "value"}
+    properties:
+      age:
+        type: integer
+        description: The number of milliseconds that have passed since this message was sent.
+        example: 4612
+required:
+  - room_id
+  - sender
+  - origin_server_ts
+  - type
+  - content
+  - depth
+  - hashes
+  - signatures