Merge branch 'develop' of github.com:matrix-org/synapse into anoa/user_param_ui_auth github/anoa/user_param_ui_auth anoa/user_param_ui_auth

* 'develop' of github.com:matrix-org/synapse: (369 commits)
  Add functions to `MultiWriterIdGen` used by events stream (#8164)
  Do not allow send_nonmember_event to be called with shadow-banned users. (#8158)
  Changelog fixes
  1.19.1rc1
  Make StreamIdGen `get_next` and `get_next_mult` async  (#8161)
  Wording fixes to 'name' user admin api filter (#8163)
  Fix missing double-backtick in RST document
  Search in columns 'name' and 'displayname' in the admin users endpoint (#7377)
  Add type hints for state. (#8140)
  Stop shadow-banned users from sending non-member events. (#8142)
  Allow capping a room's retention policy (#8104)
  Add healthcheck for default localhost 8008 port on /health endpoint. (#8147)
  Fix flaky shadow-ban tests. (#8152)
  Fix join ratelimiter breaking profile updates and idempotency (#8153)
  Do not apply ratelimiting on joins to appservices (#8139)
  Don't fail /submit_token requests on incorrect session ID if request_token_inhibit_3pid_errors is turned on (#7991)
  Do not apply ratelimiting on joins to appservices (#8139)
  Micro-optimisations to get_auth_chain_ids (#8132)
  Allow denying or shadow banning registrations via the spam checker (#8034)
  Stop shadow-banned users from sending invites. (#8095)
  ...

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+# JWT Login Type
+
+Synapse comes with a non-standard login type to support
+[JSON Web Tokens](https://en.wikipedia.org/wiki/JSON_Web_Token). In general the
+documentation for
+[the login endpoint](https://matrix.org/docs/spec/client_server/r0.6.1#login)
+is still valid (and the mechanism works similarly to the
+[token based login](https://matrix.org/docs/spec/client_server/r0.6.1#token-based)).
+
+To log in using a JSON Web Token, clients should submit a `/login` request as
+follows:
+
+```json
+{
+  "type": "org.matrix.login.jwt",
+  "token": "<jwt>"
+}
+```
+
+Note that the login type of `m.login.jwt` is supported, but is deprecated. This
+will be removed in a future version of Synapse.
+
+The `token` field should include the JSON web token with the following claims:
+
+* The `sub` (subject) claim is required and should encode the local part of the
+  user ID.
+* The expiration time (`exp`), not before time (`nbf`), and issued at (`iat`)
+  claims are optional, but validated if present.
+* The issuer (`iss`) claim is optional, but required and validated if configured.
+* The audience (`aud`) claim is optional, but required and validated if configured.
+  Providing the audience claim when not configured will cause validation to fail.
+
+In the case that the token is not valid, the homeserver must respond with
+`403 Forbidden` and an error code of `M_FORBIDDEN`.
+
+As with other login types, there are additional fields (e.g. `device_id` and
+`initial_device_display_name`) which can be included in the above request.
+
+## Preparing Synapse
+
+The JSON Web Token integration in Synapse uses the
+[`PyJWT`](https://pypi.org/project/pyjwt/) library, which must be installed
+as follows:
+
+ * The relevant libraries are included in the Docker images and Debian packages
+   provided by `matrix.org` so no further action is needed.
+
+ * If you installed Synapse into a virtualenv, run `/path/to/env/bin/pip
+   install synapse[pyjwt]` to install the necessary dependencies.
+
+ * For other installation mechanisms, see the documentation provided by the
+   maintainer.
+
+To enable the JSON web token integration, you should then add an `jwt_config` section
+to your configuration file (or uncomment the `enabled: true` line in the
+existing section). See [sample_config.yaml](./sample_config.yaml) for some
+sample settings.
+
+## How to test JWT as a developer
+
+Although JSON Web Tokens are typically generated from an external server, the
+examples below use [PyJWT](https://pyjwt.readthedocs.io/en/latest/) directly.
+
+1.  Configure Synapse with JWT logins, note that this example uses a pre-shared
+    secret and an algorithm of HS256:
+
+    ```yaml
+    jwt_config:
+        enabled: true
+        secret: "my-secret-token"
+        algorithm: "HS256"
+    ```
+2.  Generate a JSON web token:
+
+    ```bash
+    $ pyjwt --key=my-secret-token --alg=HS256 encode sub=test-user
+    eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ0ZXN0LXVzZXIifQ.Ag71GT8v01UO3w80aqRPTeuVPBIBZkYhNTJJ-_-zQIc
+    ```
+3.  Query for the login types and ensure `org.matrix.login.jwt` is there:
+
+    ```bash
+    curl http://localhost:8080/_matrix/client/r0/login
+    ```
+4.  Login used the generated JSON web token from above:
+
+    ```bash
+    $ curl http://localhost:8082/_matrix/client/r0/login -X POST \
+        --data '{"type":"org.matrix.login.jwt","token":"eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJ0ZXN0LXVzZXIifQ.Ag71GT8v01UO3w80aqRPTeuVPBIBZkYhNTJJ-_-zQIc"}'
+    {
+        "access_token": "<access token>",
+        "device_id": "ACBDEFGHI",
+        "home_server": "localhost:8080",
+        "user_id": "@test-user:localhost:8480"
+    }
+    ```
+
+You should now be able to use the returned access token to query the client API.