Improve startup logging and logging consistency

Startup log:
- Add interface, port, and fileTransferPort fields to the "Hotline
  server started" line so operators can see what the server bound to.
- Resolve an empty -interface flag to 0.0.0.0 for display.

Levels:
- Demote the two Redis startup messages (ban management, cleared online
  users) from Info to Debug.

Consistency:
- Standardize the error field key to "err" (was "Err" in a few account
  handlers) and lowercase "Account" -> "account".
- Standardize the remote-address key to "remoteAddr" (was "RemoteAddr").
- Replace fmt.Sprintf in the tracker-registration message and string
  concatenation in the config-dir-init and ban-disconnect messages with
  structured fields; use the standard "err" key.
- Give the two bare rLogger.Error(err.Error()) file-transfer calls a
  descriptive message and an "err" field.

logger.go:
- Only attach the rotating lumberjack file writer when --log-file is set.
  An empty Filename made lumberjack write to a temp file by default.

3 files changed, 7 insertions, 7 deletions

diff --git a/hotline/client_conn.go b/hotline/client_conn.go
index 9ca93a7..c17ef35 100644
--- a/hotline/client_conn.go
+++ b/hotline/client_conn.go
@@ -176,7 +176,7 @@ func (cc *ClientConn) Disconnect() {
 	}
 
 	if err := cc.Connection.Close(); err != nil {
-		cc.Server.Logger.Debug("error closing client connection", "RemoteAddr", cc.RemoteAddr)
+		cc.Server.Logger.Debug("error closing client connection", "remoteAddr", cc.RemoteAddr)
 	}
 }
 
diff --git a/hotline/file_transfer.go b/hotline/file_transfer.go
index 98999f1..86e10eb 100644
--- a/hotline/file_transfer.go
+++ b/hotline/file_transfer.go
@@ -477,7 +477,7 @@ func DownloadFolderHandler(rwc io.ReadWriter, fullPath string, fileTransfer *Fil
 
 		// Send file size to client
 		if _, err := rwc.Write(hlFile.Ffo.TransferSize(dataOffset)); err != nil {
-			rLogger.Error(err.Error())
+			rLogger.Error("Error sending file size", "err", err)
 			return fmt.Errorf("error sending file size: %w", err)
 		}
 
@@ -625,7 +625,7 @@ func UploadFolderHandler(rwc io.ReadWriter, fullPath string, fileTransfer *FileT
 				}
 
 				if err := receiveFile(rwc, file, io.Discard, io.Discard, fileTransfer.bytesSentCounter); err != nil {
-					rLogger.Error(err.Error())
+					rLogger.Error("Error receiving file", "err", err)
 				}
 
 				err = os.Rename(fullPath+"/"+fu.FormattedPath()+".incomplete", fullPath+"/"+fu.FormattedPath())
diff --git a/hotline/server.go b/hotline/server.go
index 7bc6a4a..6ac68d8 100644
--- a/hotline/server.go
+++ b/hotline/server.go
@@ -309,16 +309,16 @@ func (s *Server) Serve(ctx context.Context, ln net.Listener) error {
 
 				// Check if the rate limit is exceeded and close the connection if so.
 				if !rl.Allow() {
-					s.Logger.Info("Rate limit exceeded", "RemoteAddr", conn.RemoteAddr())
+					s.Logger.Info("Rate limit exceeded", "remoteAddr", conn.RemoteAddr())
 					_ = conn.Close()
 					return
 				}
 
 				if err := s.handleNewConnection(connCtx, conn, conn.RemoteAddr().String()); err != nil {
 					if err == io.EOF {
-						s.Logger.Info("Client disconnected", "RemoteAddr", conn.RemoteAddr())
+						s.Logger.Info("Client disconnected", "remoteAddr", conn.RemoteAddr())
 					} else {
-						s.Logger.Error("Error serving request", "RemoteAddr", conn.RemoteAddr(), "err", err)
+						s.Logger.Error("Error serving request", "remoteAddr", conn.RemoteAddr(), "err", err)
 					}
 				}
 			}()
@@ -380,7 +380,7 @@ func (s *Server) registerWithAllTrackers() {
 		tr.Password = parseTrackerPassword(t)
 
 		if err := s.TrackerRegistrar.Register(t, tr); err != nil {
-			s.Logger.Error(fmt.Sprintf("Unable to register with tracker %v", t), "error", err)
+			s.Logger.Error("Unable to register with tracker", "tracker", t, "err", err)
 		}
 	}
 }