Refactor WebRTC exception messages and fingerprint comparison (#1661)

* Refactor WebRTC exception messages and fingerprint comparison

Consolidate exception message formatting to single lines for clarity.
Update certificate fingerprint comparison to use string.Equals with
ordinal ignore case, following best practices and user preferences.

* Fix extra spaces in RTCDataChannel exception messages

Removed unnecessary double spaces in exception strings to improve consistency and readability in RTCDataChannel.cs.

Author: paulomorgado

src/SIPSorcery/net/WebRTC/RTCDataChannel.cs

@@ -134,8 +134,7 @@ public void send(string message)
         {
             if (message != null && Encoding.UTF8.GetByteCount(message) > _transport.maxMessageSize)
             {
-                throw new ApplicationException($"Data channel {label} was requested to send data of length {Encoding.UTF8.GetByteCount(message)} " +
-                    $" that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
+                throw new ApplicationException($"Data channel {label} was requested to send data of length {Encoding.UTF8.GetByteCount(message)} that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
             }
             else if (_transport.state != RTCSctpTransportState.Connected)
             {
@@ -173,8 +172,7 @@ public void send(byte[] data, int offset = 0, int count = -1)
 
             if (effectiveCount > _transport.maxMessageSize)
             {
-                throw new ApplicationException($"Data channel {label} was requested to send data of length {effectiveCount} " +
-                    $" that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
+                throw new ApplicationException($"Data channel {label} was requested to send data of length {effectiveCount} that exceeded the maximum allowed message size of {_transport.maxMessageSize}.");
             }
             else if (_transport.state != RTCSctpTransportState.Connected)
             {

src/SIPSorcery/net/WebRTC/RTCPeerConnection.cs

@@ -1876,12 +1876,13 @@ private bool DoDtlsHandshake(DtlsSrtpTransport dtlsHandle)
             }
             else
             {
-                logger.LogDebug($"RTCPeerConnection DTLS handshake result {handshakeResult}, is handshake complete {dtlsHandle.IsHandshakeComplete()}.");
+                logger.LogDebug("RTCPeerConnection DTLS handshake result {HandshakeResult}, is handshake complete {IsHandshakeComplete}.",
+                    handshakeResult, dtlsHandle.IsHandshakeComplete());
 
                 var expectedFp = RemotePeerDtlsFingerprint;
                 var remoteFingerprint = DtlsUtils.Fingerprint(expectedFp.algorithm, dtlsHandle.GetRemoteCertificate().GetCertificateAt(0));
 
-                if (remoteFingerprint.value?.ToUpper() != expectedFp.value?.ToUpper())
+                if (!string.Equals(remoteFingerprint.value, expectedFp.value, StringComparison.OrdinalIgnoreCase))
                 {
                     logger.LogWarning("RTCPeerConnection remote certificate fingerprint mismatch, expected {ExpectedFingerprint}, actual {RemoteFingerprint}.", expectedFp, remoteFingerprint);
                     Close("dtls fingerprint mismatch");

src/SIPSorcery/net/WebRTC/RTCSctpTransport.cs

@@ -380,8 +380,7 @@ public override void Send(string associationID, byte[] buffer, int offset, int l
         {
             if (length > maxMessageSize)
             {
-                throw new ApplicationException($"RTCSctpTransport was requested to send data of length {length} " +
-                    $" that exceeded the maximum allowed message size of {maxMessageSize}.");
+                throw new ApplicationException($"RTCSctpTransport was requested to send data of length {length}  that exceeded the maximum allowed message size of {maxMessageSize}.");
             }
 
             if (!_isClosed)