allow plugins to customize if they run on startup

Author: tayloraswift

Sources/UnidocServer/Plugins/Unidoc.Plugin.swift

@@ -15,11 +15,16 @@ extension Unidoc
         static var title:String { get }
         static var id:String { get }
 
+        var enabledInitially:Bool { get }
+
         func run(in context:PluginContext<Event>) async throws -> Duration?
     }
 }
 extension Unidoc.Plugin
 {
+    @inlinable public
+    var enabledInitially:Bool { true }
+
     @inlinable public
     static var cooldown:Duration { .seconds(5) }
 }

Sources/UnidocServer/Plugins/Unidoc.PluginHandle.swift

@@ -10,7 +10,7 @@ extension Unidoc
         init(plugin:any Plugin)
         {
             self.plugin = plugin
-            self.active = .init(true)
+            self.active = .init(plugin.enabledInitially)
         }
     }
 }