Allow custom data folder

Sources/App/Management/Configuration.swift

@@ -23,6 +23,13 @@ struct Configuration {
         /// The number of minutes until a password reset token is no longer valid
         let tokenExpiryDuration: Int
     }
+    
+    /**
+     The folder where the data should be stored.
+     
+     If the folder is set to `nil`, then the `Resources` folder is used.
+     */
+    let dataDirectory: String?
 
     /// The authentication tokens to access the metrics
     let monitoringTokens: Set<String>
@@ -42,6 +49,13 @@ struct Configuration {
         }
         return resourcesDirectory.appendingPathComponent(logPath)
     }
+    
+    func customDataDirectory(or publicDirectory: String) -> URL {
+        guard let dataDirectory else {
+            return URL(fileURLWithPath: publicDirectory)
+        }
+        return URL(fileURLWithPath: dataDirectory)
+    }
 }
 
 extension Configuration {