Feature/maintenance (#916)

* Maintenance mode
* fix(hls): release origin slot before next origin I/O

backend/app/src/api/api_utils/mod.rs

@@ -240,6 +240,7 @@ mod auth;
 mod catchup;
 mod clock;
 mod local_files;
+mod maintenance;
 mod media_server;
 mod metering;
 mod provider_acquire;
@@ -324,6 +325,7 @@ pub(crate) use self::{
     auth::{input_for_user, with_recording_headers},
     catchup::get_catchup_session_ttl_secs,
     local_files::local_stream_response,
+    maintenance::{blocks_new_playback, is_running_playback, maintenance_rejection_response},
     provider_acquire::{acquire_exact_provider_handle, stream_response_with_provider_handle},
     provider_urls::select_provider_stream_url,
     resources::force_hls_resource_response,