Work on failed outbound requests and move type migrators

- DB type migrators are now in separate file, in preparation for full
  custom sql migration statements
- Start work on handling failed outbound requests stored in the db

storage-new/models/FailedOutboundRequests.go

@@ -16,3 +16,17 @@ type FailedOutboundRequest struct {
 	TargetServer      *RemoteServer // The remote server being targeted. Included to determine if a request still has a chance of success
 	TargetServerId    uint          // Id of the target remote server
 }
+
+type IFailedOutboundRequest interface {
+	// KillServers marks all servers where a request has more than X failed attempts as dead
+	//
+	// WITH servers_to_kill AS (
+	//   SELECT target_server_id
+	//   FROM failed_outbound_requests
+	//   WHERE nr_of_attempts > @maxAttempts
+	// )
+	// UPDATE remote_servers
+	// SET is_dead = true
+	// WHERE id IN (SELECT target_server_id FROM servers_to_kill)
+	KillServers(maxAttempts uint32) error
+}

storage-new/models/ServerMetadata.go

@@ -12,6 +12,7 @@ type ServerMetadata struct {
 	UpdatedAt time.Time
 
 	// ---- Section TLS LetsEncrypt
+
 	LEDomain            string
 	LECertUrl           string
 	LECertStableUrl     string
@@ -21,4 +22,7 @@ type ServerMetadata struct {
 	LECSR               []byte // Encrypted
 	LELastUpdate        sql.NullTime
 	LEUserPrivKey       []byte // Encrypted
+
+	// ---- Section Database
+	LastMigrationVersion uint64
 }