Update docs for older appservice bridges to enable legacy authorization (#2841)

* Update docs for older appservice bridges to enable legacy authorization

* Update docs/configuring-playbook-bridge-appservice-discord.md

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* Update docs/configuring-playbook-bridge-appservice-webhooks.md

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* further fix formatting

---------

Co-authored-by: blotree <teruyo@touhou-project.com>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

docs/configuring-playbook-bridge-appservice-discord.md

@@ -1,7 +1,7 @@
 # Setting up Appservice Discord (optional)
 
-**Note**: bridging to [Discord](https://discordapp.com/) can also happen via the [mx-puppet-discord](configuring-playbook-bridge-mx-puppet-discord.md) and [mautrix-discord](configuring-playbook-bridge-mautrix-discord.md) bridges supported by the playbook.   
-- For using as a Bot we are recommend the Appservice Discord bridge (the one being discussed here), because it supports plumbing.  
+**Note**: bridging to [Discord](https://discordapp.com/) can also happen via the [mx-puppet-discord](configuring-playbook-bridge-mx-puppet-discord.md) and [mautrix-discord](configuring-playbook-bridge-mautrix-discord.md) bridges supported by the playbook.
+- For using as a Bot we are recommend the Appservice Discord bridge (the one being discussed here), because it supports plumbing.
 - For personal use we recommend the [mautrix-discord](configuring-playbook-bridge-mautrix-discord.md) bridge, because it is the most fully-featured and stable of the 3 Discord bridges supported by the playbook.
 
 The playbook can install and configure [matrix-appservice-discord](https://github.com/Half-Shot/matrix-appservice-discord) for you.
@@ -23,8 +23,14 @@ matrix_appservice_discord_enabled: true
 matrix_appservice_discord_client_id: "YOUR DISCORD APP CLIENT ID"
 matrix_appservice_discord_bot_token: "YOUR DISCORD APP BOT TOKEN"
 ```
+5. As of Synapse 1.90.0, you will need to add the following to `matrix_synapse_configuration_extension_yaml` to enable the [backwards compatibility](https://matrix-org.github.io/synapse/latest/upgrade#upgrading-to-v1900) that this bridge needs:
+```yaml
+matrix_synapse_configuration_extension_yaml: |
+  use_appservice_legacy_authorization: true
+```
+*Note*: This deprecated method is considered insecure.
 
-5. If you've already installed Matrix services using the playbook before, you'll need to re-run it (`--tags=setup-all,start`). If not, proceed with [configuring other playbook services](configuring-playbook.md) and then with [Installing](installing.md). Get back to this guide once ready.
+6. If you've already installed Matrix services using the playbook before, you'll need to re-run it (`--tags=setup-all,start`). If not, proceed with [configuring other playbook services](configuring-playbook.md) and then with [Installing](installing.md). Get back to this guide once ready.
 
 Other configuration options are available via the `matrix_appservice_discord_configuration_extension_yaml` variable.
 

docs/configuring-playbook-bridge-appservice-webhooks.md

@@ -26,22 +26,29 @@ you can adjust this in `inventory/host_vars/matrix.<domain-name>/vars.yml` as we
 matrix_appservice_webhooks_log_level: '<log_level>'
 ```
 
-3. If you've already installed Matrix services using the playbook before, you'll need to re-run it (`--tags=setup-all,start`). If not, proceed with [configuring other playbook services](configuring-playbook.md) and then with [Installing](installing.md). Get back to this guide once ready.
+3. As of Synapse 1.90.0, you will need to add the following to `matrix_synapse_configuration_extension_yaml` to enable the [backwards compatibility](https://matrix-org.github.io/synapse/latest/upgrade#upgrading-to-v1900) that this bridge needs:
+```yaml
+matrix_synapse_configuration_extension_yaml: |
+  use_appservice_legacy_authorization: true
+```
+*Note*: This deprecated method is considered insecure.
+
+4. If you've already installed Matrix services using the playbook before, you'll need to re-run it (`--tags=setup-all,start`). If not, proceed with [configuring other playbook services](configuring-playbook.md) and then with [Installing](installing.md). Get back to this guide once ready.
 
-4. If you're using the [Dimension Integration Manager](configuring-playbook-dimension.md), you can configure the Webhooks bridge by opening the Dimension integration manager -> Settings -> Bridges and selecting edit action for "Webhook Bridge". Press "Add self-hosted Bridge" button and populate "Provisioning URL"  & "Shared Secret" values from `/matrix/appservice-webhooks/config/config.yaml` file's homeserver URL value and provisioning secret value, respectively. 
+5. If you're using the [Dimension Integration Manager](configuring-playbook-dimension.md), you can configure the Webhooks bridge by opening the Dimension integration manager -> Settings -> Bridges and selecting edit action for "Webhook Bridge". Press "Add self-hosted Bridge" button and populate "Provisioning URL"  & "Shared Secret" values from `/matrix/appservice-webhooks/config/config.yaml` file's homeserver URL value and provisioning secret value, respectively.
 
-5. Invite the bridge bot user to your room:
+6. Invite the bridge bot user to your room:
 
     - either with `/invite @_webhook:<domain.name>` (*Note*: Make sure you have administration permissions in your room)
 
     - or simply add the bridge bot to a private channel (personal channels imply you being an administrator)
 
-6. Send a message to the bridge bot in order to receive a private message including the webhook link.
+7. Send a message to the bridge bot in order to receive a private message including the webhook link.
 ```
 !webhook
 ```
 
-7. The JSON body for posting messages will have to look like this:
+8. The JSON body for posting messages will have to look like this:
 ```json
 {
     "text": "Hello world!",