add /openid/request_token and /openid/userinfo routes

heavily changed and improved by me

Co-authored-by: mikoto <avdb@keemail.me>
Signed-off-by: strawberry <strawberry@puppygock.gay>

src/api/server/openid.rs

@@ -0,0 +1,16 @@
+use ruma::api::federation::openid::get_openid_userinfo;
+
+use crate::{services, Result, Ruma};
+
+/// # `GET /_matrix/federation/v1/openid/userinfo`
+///
+/// Get information about the user that generated the OpenID token.
+pub(crate) async fn get_openid_userinfo_route(
+	body: Ruma<get_openid_userinfo::v1::Request>,
+) -> Result<get_openid_userinfo::v1::Response> {
+	Ok(get_openid_userinfo::v1::Response::new(
+		services()
+			.users
+			.find_from_openid_token(&body.access_token)?,
+	))
+}