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>

8 files changed, 9 insertions, 9 deletions

diff --git a/docs/admin_api/account_validity.md b/docs/admin_api/account_validity.md
index d878bf7451..87d8f7150e 100644
--- a/docs/admin_api/account_validity.md
+++ b/docs/admin_api/account_validity.md
@@ -5,7 +5,7 @@ use it, you must enable the account validity feature (under
 `account_validity`) in Synapse's configuration.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 ## Renew account
 
diff --git a/docs/admin_api/event_reports.md b/docs/admin_api/event_reports.md
index be6f0961bf..beec8bb7ef 100644
--- a/docs/admin_api/event_reports.md
+++ b/docs/admin_api/event_reports.md
@@ -3,7 +3,7 @@
 This API returns information about reported events.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 The api is:
 ```
diff --git a/docs/admin_api/media_admin_api.md b/docs/admin_api/media_admin_api.md
index d57c5aedae..7f8c8e22c1 100644
--- a/docs/admin_api/media_admin_api.md
+++ b/docs/admin_api/media_admin_api.md
@@ -6,7 +6,7 @@ Details about the format of the `media_id` and storage of the media in the file
 are documented under [media repository](../media_repository.md).
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 ## List all media in a room
 
diff --git a/docs/admin_api/purge_history_api.md b/docs/admin_api/purge_history_api.md
index 2527e2758b..ba6d08aa4d 100644
--- a/docs/admin_api/purge_history_api.md
+++ b/docs/admin_api/purge_history_api.md
@@ -11,7 +11,7 @@ Note that Synapse requires at least one message in each room, so it will never
 delete the last message in a room.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 The API is:
 
diff --git a/docs/admin_api/room_membership.md b/docs/admin_api/room_membership.md
index 310d6ae628..94bc95a8d5 100644
--- a/docs/admin_api/room_membership.md
+++ b/docs/admin_api/room_membership.md
@@ -6,7 +6,7 @@ local users. The server administrator must be in the room and have permission to
 invite users.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 ## Parameters
 
diff --git a/docs/admin_api/rooms.md b/docs/admin_api/rooms.md
index 8f727b363e..66b29e82dc 100644
--- a/docs/admin_api/rooms.md
+++ b/docs/admin_api/rooms.md
@@ -5,7 +5,7 @@ server. There are various parameters available that allow for filtering and
 sorting the returned list. This API supports pagination.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 **Parameters**
 
@@ -400,7 +400,7 @@ sent to a room in a given timeframe. There are various parameters available
 that allow for filtering and ordering the returned list. This API supports pagination.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 This endpoint mirrors the [Matrix Spec defined Messages API](https://spec.matrix.org/v1.1/client-server-api/#get_matrixclientv3roomsroomidmessages).
 
diff --git a/docs/admin_api/statistics.md b/docs/admin_api/statistics.md
index a26c76f9f3..03b3621e55 100644
--- a/docs/admin_api/statistics.md
+++ b/docs/admin_api/statistics.md
@@ -4,7 +4,7 @@ Returns information about all local media usage of users. Gives the
 possibility to filter them by time and user.
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 The API is:
 
diff --git a/docs/admin_api/user_admin_api.md b/docs/admin_api/user_admin_api.md
index 880bef4194..86c29ab380 100644
--- a/docs/admin_api/user_admin_api.md
+++ b/docs/admin_api/user_admin_api.md
@@ -1,7 +1,7 @@
 # User Admin API
 
 To use it, you will need to authenticate by providing an `access_token`
-for a server admin: see [Admin API](../usage/administration/admin_api).
+for a server admin: see [Admin API](../usage/administration/admin_api/).
 
 ## Query User Account