Fix broken links in the Synapse documentation. (#14744)

* Fix stale external links

* Fix some internal links

* Fix URLs without trailing / where needed

* Fix more links

* Newsfile

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

* Reapply docs/openid.md fix after conflict

Signed-off-by: Olivier Wilkinson (reivilibre) <oliverw@matrix.org>

docs/usage/administration/admin_api/README.md

@@ -7,7 +7,7 @@ server admin. (Note that a server admin is distinct from a room admin.)
 
 An existing user can be marked as a server admin by updating the database directly.
 
-Check your [database settings](config_documentation.md#database) in the configuration file, connect to the correct database using either `psql [database name]` (if using PostgreSQL) or `sqlite3 path/to/your/database.db` (if using SQLite) and elevate the user `@foo:bar.com` to administrator.
+Check your [database settings](../../configuration/config_documentation.md#database) in the configuration file, connect to the correct database using either `psql [database name]` (if using PostgreSQL) or `sqlite3 path/to/your/database.db` (if using SQLite) and elevate the user `@foo:bar.com` to administrator.
 ```sql
 UPDATE users SET admin = 1 WHERE name = '@foo:bar.com';
 ```
@@ -32,10 +32,10 @@ curl --header "Authorization: Bearer <access_token>" <the_rest_of_your_API_reque
 ```
 
 For example, suppose we want to
-[query the account](user_admin_api.md#query-user-account) of the user
+[query the account](../../../admin_api/user_admin_api.md#query-user-account) of the user
 `@foo:bar.com`. We need an admin access token (e.g.
 `syt_AjfVef2_L33JNpafeif_0feKJfeaf0CQpoZk`), and we need to know which port
-Synapse's [`client` listener](config_documentation.md#listeners) is listening
+Synapse's [`client` listener](../../configuration/config_documentation.md#listeners) is listening
 on (e.g. `8008`). Then we can use the following command to request the account
 information from the Admin API.
 

docs/usage/administration/admin_api/federation.md

@@ -81,7 +81,7 @@ The following fields are returned in the JSON response body:
   - `failure_ts` - nullable integer - The first time Synapse tried and failed to reach the
     remote server, in ms. This is `null` if communication with the remote server has never failed.
   - `last_successful_stream_ordering` - nullable integer - The stream ordering of the most
-    recent successfully-sent [PDU](understanding_synapse_through_grafana_graphs.md#federation)
+    recent successfully-sent [PDU](../understanding_synapse_through_grafana_graphs.md#federation)
     to this destination, or `null` if this information has not been tracked yet.
 - `next_token`: string representing a positive integer - Indication for pagination. See above.
 - `total` - integer - Total number of destinations.
@@ -174,7 +174,7 @@ The following fields are returned in the JSON response body:
   Room objects contain the following fields:
   - `room_id` - string - The ID of the room.
   - `stream_ordering` - integer -  The stream ordering of the most recent
-    successfully-sent [PDU](understanding_synapse_through_grafana_graphs.md#federation)
+    successfully-sent [PDU](../understanding_synapse_through_grafana_graphs.md#federation)
     to this destination in this room.
 - `next_token`: string representing a positive integer - Indication for pagination. See above.
 - `total` - integer - Total number of destinations.

docs/usage/administration/admin_api/registration_tokens.md

@@ -6,7 +6,7 @@ registration requests, as proposed in
 and stabilised in version 1.2 of the Matrix specification.
 To use it, you will need to enable the `registration_requires_token` config
 option, and authenticate by providing an `access_token` for a server admin:
-see [Admin API](../admin_api).
+see [Admin API](../admin_api/).
 
 
 ## Registration token objects

docs/usage/administration/admin_faq.md

@@ -2,7 +2,7 @@
 
 How do I become a server admin?
 ---
-If your server already has an admin account you should use the [User Admin API](../../admin_api/user_admin_api.md#Change-whether-a-user-is-a-server-administrator-or-not) to promote other accounts to become admins.
+If your server already has an admin account you should use the [User Admin API](../../admin_api/user_admin_api.md#change-whether-a-user-is-a-server-administrator-or-not) to promote other accounts to become admins.
 
 If you don't have any admin accounts yet you won't be able to use the admin API, so you'll have to edit the database manually. Manually editing the database is generally not recommended so once you have an admin account: use the admin APIs to make further changes.
 
@@ -115,7 +115,7 @@ something like the following in their logs:
 
     2019-09-11 19:32:04,271 - synapse.federation.transport.server - 288 - WARNING - GET-11752 - authenticate_request failed: 401: Invalid signature for server <server> with key ed25519:a_EqML: Unable to verify signature for <server>
 
-This is normally caused by a misconfiguration in your reverse-proxy. See [the reverse proxy docs](docs/reverse_proxy.md) and double-check that your settings are correct.
+This is normally caused by a misconfiguration in your reverse-proxy. See [the reverse proxy docs](../../reverse_proxy.md) and double-check that your settings are correct.
 
 
 Help!! Synapse is slow and eats all my RAM/CPU!

docs/usage/administration/monitoring/reporting_homeserver_usage_statistics.md

@@ -78,4 +78,4 @@ If you would like to set up your own statistics collection server and send metri
 consider using one of the following known implementations:
 
 * [Matrix.org's Panopticon](https://github.com/matrix-org/panopticon)
-* [Famedly's Barad-dûr](https://gitlab.com/famedly/company/devops/services/barad-dur)
+* [Famedly's Barad-dûr](https://gitlab.com/famedly/infra/services/barad-dur)

docs/usage/administration/request_log.md

@@ -1,6 +1,6 @@
 # Request log format
 
-HTTP request logs are written by synapse (see [`site.py`](../synapse/http/site.py) for details).
+HTTP request logs are written by synapse (see [`synapse/http/site.py`](https://github.com/matrix-org/synapse/tree/develop/synapse/http/site.py) for details).
 
 See the following for how to decode the dense data available from the default logging configuration.