fix(server): start job workers after DB (#17806)

Job workers are currently started on app init, which means they are started
before the DB is initialised. This can be problematic if jobs which need to use
the DB start running before it's ready. It also means that swapping out the
queue implementation for something which uses the DB won't work.

server/src/enum.ts

@@ -407,6 +407,8 @@ export enum DatabaseExtension {
 export enum BootstrapEventPriority {
   // Database service should be initialized before anything else, most other services need database access
   DatabaseService = -200,
+  // Other services may need to queue jobs on bootstrap.
+  JobService = -190,
   // Initialise config after other bootstrap services, stop other services from using config on bootstrap
   SystemConfig = 100,
 }