add registration token validity endpoint as per matrix 1.2

Signed-off-by: strawberry <strawberry@puppygock.gay>

src/api/client_server/account.rs

@@ -4,7 +4,7 @@ use register::RegistrationKind;
 use ruma::{
 	api::client::{
 		account::{
-			change_password, deactivate, get_3pids, get_username_availability,
+			change_password, check_registration_token_validity, deactivate, get_3pids, get_username_availability,
 			register::{self, LoginType},
 			request_3pid_management_token_via_email, request_3pid_management_token_via_msisdn, whoami,
 			ThirdPartyIdRemovalStatus,
@@ -594,3 +594,24 @@ pub(crate) async fn request_3pid_management_token_via_msisdn_route(
 		"Third party identifier is not allowed",
 	))
 }
+
+/// # `GET /_matrix/client/v1/register/m.login.registration_token/validity`
+///
+/// Checks if the provided registration token is valid at the time of checking
+///
+/// Currently does not have any ratelimiting, and this isn't very practical as
+/// there is only one registration token allowed.
+pub(crate) async fn check_registration_token_validity(
+	body: Ruma<check_registration_token_validity::v1::Request>,
+) -> Result<check_registration_token_validity::v1::Response> {
+	let Some(reg_token) = services().globals.config.registration_token.clone() else {
+		return Err(Error::BadRequest(
+			ErrorKind::forbidden(),
+			"Server does not allow token registration.",
+		));
+	};
+
+	Ok(check_registration_token_validity::v1::Response {
+		valid: reg_token == body.token,
+	})
+}

src/api/router.rs

@@ -28,6 +28,7 @@ pub fn build(router: Router, server: &Server) -> Router {
 		.ruma_route(client_server::third_party_route)
 		.ruma_route(client_server::request_3pid_management_token_via_email_route)
 		.ruma_route(client_server::request_3pid_management_token_via_msisdn_route)
+		.ruma_route(client_server::check_registration_token_validity)
 		.ruma_route(client_server::get_capabilities_route)
 		.ruma_route(client_server::get_pushrules_all_route)
 		.ruma_route(client_server::set_pushrule_route)