Fix error / info logging around AP mentions

This fixes log formatting and makes verbiage consistent & concise.

database.go

@@ -2618,21 +2618,21 @@ func (db *datastore) GetProfilePageFromHandle(app *App, handle string) (string,
 		if errRemoteUser == nil {
 			_, err := app.db.Exec("UPDATE remoteusers SET handle = ? WHERE actor_id = ?", handle, actorIRI)
 			if err != nil {
-				log.Error("Can't update handle (" + handle + ") in database for user " + actorIRI)
+				log.Error("Couldn't update handle '%s' for user %s", handle, actorIRI)
 			}
 		} else {
 			// this probably means we don't have the user in the table so let's try to insert it
 			// here we need to ask the server for the inboxes
 			remoteActor, err := activityserve.NewRemoteActor(actorIRI)
 			if err != nil {
-				log.Error("Couldn't fetch remote actor", err)
+				log.Error("Couldn't fetch remote actor: %v", err)
 			}
 			if debugging {
 				log.Info("%s %s %s %s", actorIRI, remoteActor.GetInbox(), remoteActor.GetSharedInbox(), handle)
 			}
 			_, err = app.db.Exec("INSERT INTO remoteusers (actor_id, inbox, shared_inbox, handle) VALUES(?, ?, ?, ?)", actorIRI, remoteActor.GetInbox(), remoteActor.GetSharedInbox(), handle)
 			if err != nil {
-				log.Error("Can't insert remote user in database", err)
+				log.Error("Couldn't insert remote user: %v", err)
 				return "", err
 			}
 		}

posts.go

@@ -1181,7 +1181,7 @@ func (p *PublicPost) ActivityObject(app *App) *activitystreams.Object {
 	for _, handle := range mentions {
 		actorIRI, err := app.db.GetProfilePageFromHandle(app, handle)
 		if err != nil {
-			log.Info("Can't find this user either in the database nor in the remote instance")
+			log.Info("Couldn't find this user locally or remotely")
 			continue
 		}
 		mentionedUsers[handle] = actorIRI

webfinger.go

@@ -101,20 +101,20 @@ func RemoteLookup(handle string) string {
 	parts := strings.Split(handle, "@")
 	resp, err := http.Get("https://" + parts[1] + "/.well-known/webfinger?resource=acct:" + handle)
 	if err != nil {
-		log.Error("Error performing webfinger request", err)
+		log.Error("Error on webfinger request: %v", err)
 		return ""
 	}
 
 	body, err := ioutil.ReadAll(resp.Body)
 	if err != nil {
-		log.Error("Error reading webfinger response", err)
+		log.Error("Error on webfinger response: %v", err)
 		return ""
 	}
 
 	var result webfinger.Resource
 	err = json.Unmarshal(body, &result)
 	if err != nil {
-		log.Error("Unsupported webfinger response received: %v", err)
+		log.Error("Unable to parse webfinger response: %v", err)
 		return ""
 	}