Try to fix /_matrix/client/v3 for ma1sd via URL rewriting to (/_matrix/client/r0)

Hopefully fixes: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2954

Untested.

Patch inspired by: https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2954#issuecomment-1795029963

roles/custom/matrix-nginx-proxy/defaults/main.yml

@@ -331,6 +331,12 @@ matrix_nginx_proxy_proxy_matrix_user_directory_search_enabled: false
 matrix_nginx_proxy_proxy_matrix_user_directory_search_addr_with_container: "matrix-ma1sd:{{ matrix_ma1sd_container_port }}"
 matrix_nginx_proxy_proxy_matrix_user_directory_search_addr_sans_container: "127.0.0.1:{{ matrix_ma1sd_container_port }}"
 
+# Controls whether the user directory search API will be URL-rewritten (/_matrix/client/v3/user_directory/search -> /_matrix/client/r0/user_directory/search).
+# This is to assist identity servers which only handle the r0 endpoints.
+# The v3 endpoints are the same (spec-wise), so they can usually be redirected without downsides.
+# If this is disabled, API requests will be forwarded as-is, without any URL rewriting.
+matrix_nginx_proxy_proxy_matrix_user_directory_search_v3_to_r0_redirect_enabled: true
+
 # Controls whether proxying for 3PID-based registration (`/_matrix/client/r0/register/(email|msisdn)/requestToken`) should be done (on the matrix domain).
 # This allows another service to control registrations involving 3PIDs.
 # To learn more, see: https://github.com/ma1uta/ma1sd/blob/master/docs/features/registration.md
@@ -338,6 +344,12 @@ matrix_nginx_proxy_proxy_matrix_3pid_registration_enabled: false
 matrix_nginx_proxy_proxy_matrix_3pid_registration_addr_with_container: "matrix-ma1sd:{{ matrix_ma1sd_container_port }}"
 matrix_nginx_proxy_proxy_matrix_3pid_registration_addr_sans_container: "127.0.0.1:{{ matrix_ma1sd_container_port }}"
 
+# Controls whether the user directory search API will be URL-rewritten (/_matrix/client/v3/register/(email|msisdn)/requestToken -> /_matrix/client/r0/register/(email|msisdn)/requestToken).
+# This is to assist identity servers which only handle the r0 endpoints.
+# The v3 endpoints are the same (spec-wise), so they can usually be redirected without downsides.
+# If this is disabled, API requests will be forwarded as-is, without any URL rewriting.
+matrix_nginx_proxy_proxy_matrix_3pid_registration_v3_to_r0_redirect_enabled: true
+
 # Controls whether proxying for the Identity API (`/_matrix/identity`) should be done (on the matrix domain)
 matrix_nginx_proxy_proxy_matrix_identity_api_enabled: false
 matrix_nginx_proxy_proxy_matrix_identity_api_addr_with_container: "matrix-ma1sd:{{ matrix_ma1sd_container_port }}"

roles/custom/matrix-nginx-proxy/templates/nginx/conf.d/matrix-domain.conf.j2

@@ -186,6 +186,10 @@
 
 	{% if matrix_nginx_proxy_proxy_matrix_user_directory_search_enabled %}
 	location ^~ /_matrix/client/(r0|v3)/user_directory/search {
+		{% if matrix_nginx_proxy_proxy_matrix_user_directory_search_v3_to_r0_redirect_enabled %}
+		rewrite ^(.*?)/v3/(.*?)$  $1/r0/$2 break;
+		{% endif %}
+
 		{% if matrix_nginx_proxy_enabled %}
 			{# Use the embedded DNS resolver in Docker containers to discover the service #}
 			resolver {{ matrix_nginx_proxy_http_level_resolver }} valid=5s;
@@ -203,6 +207,10 @@
 
 	{% if matrix_nginx_proxy_proxy_matrix_3pid_registration_enabled %}
 	location ~ ^/_matrix/client/(r0|v3)/register/(email|msisdn)/requestToken$ {
+		{% if matrix_nginx_proxy_proxy_matrix_3pid_registration_v3_to_r0_redirect_enabled %}
+		rewrite ^(.*?)/v3/(.*?)$  $1/r0/$2 break;
+		{% endif %}
+
 		{% if matrix_nginx_proxy_enabled %}
 			{# Use the embedded DNS resolver in Docker containers to discover the service #}
 			resolver {{ matrix_nginx_proxy_http_level_resolver }} valid=5s;