hide global services jank in service module

Mainly to make it easier to initialize the SERVICES global correctly in
more than one place.

Also this stuff really shouldn't live at the crate root anyway.

src/service.rs

@@ -1,6 +1,6 @@
 use std::{
     collections::{BTreeMap, HashMap},
-    sync::{Arc, Mutex as StdMutex},
+    sync::{Arc, Mutex as StdMutex, RwLock as StdRwLock},
 };
 
 use lru_cache::LruCache;
@@ -22,6 +22,16 @@ pub(crate) mod transaction_ids;
 pub(crate) mod uiaa;
 pub(crate) mod users;
 
+static SERVICES: StdRwLock<Option<&'static Services>> = StdRwLock::new(None);
+
+/// Convenient access to the global [`Services`] instance
+pub(crate) fn services() -> &'static Services {
+    SERVICES
+        .read()
+        .unwrap()
+        .expect("SERVICES should be initialized when this is called")
+}
+
 pub(crate) struct Services {
     pub(crate) appservice: appservice::Service,
     pub(crate) pusher: pusher::Service,
@@ -154,6 +164,11 @@ impl Services {
         })
     }
 
+    /// Installs `self` to be globally accessed via [`services`]
+    pub(crate) fn install(self) {
+        *SERVICES.write().unwrap() = Some(Box::leak(Box::new(self)));
+    }
+
     async fn memory_usage(&self) -> String {
         let lazy_load_waiting =
             self.rooms.lazy_loading.lazy_load_waiting.lock().await.len();