Add matrix-synapse-rest-auth support

docs/configuring-playbook-rest-auth.md

@@ -0,0 +1,15 @@
+# Setting up the REST authentication password provider module
+
+The playbook can now install and configure [matrix-synapse-rest-auth](https://github.com/kamax-io/matrix-synapse-rest-auth) for you.
+
+See that project's documentation to learn what it does and why it might be useful to you.
+
+If you decide that you'd like to let this playbook install it for you, you need soem configuration like this:
+
+```yaml
+matrix_synapse_ext_password_provider_rest_auth_enabled: true
+matrix_synapse_ext_password_provider_rest_auth_endpoint: "http://change.me.example.com:12345"
+matrix_synapse_ext_password_provider_rest_auth_registration_enforce_lowercase: false
+matrix_synapse_ext_password_provider_rest_auth_registration_profile_name_autofill: true
+matrix_synapse_ext_password_provider_rest_auth_login_profile_name_autofill: false
+```

docs/configuring-playbook.md

@@ -31,4 +31,6 @@ When you're done with all the configuration you'd like to do, continue with [Ins
 
 - [Adjusting mxisd Identity Server configuration](configuring-playbook-mxisd.md) (optional)
 
-- [Using your own webserver, instead of this playbook's nginx proxy](configuring-playbook-own-webserver.md) (optional)
+- [Using your own webserver, instead of this playbook's nginx proxy](configuring-playbook-own-webserver.md) (optional)
+
+- [Setting up the REST authentication password provider module](configuring-playbook-rest-auth.md) (optional)