Fix buffer reuse issue in WebSockets

[mdaneri]

Description:
This pull request addresses issue [#1527] by modifying the way buffers are managed in PodeSignalRequest. The problem was that the base class, PodeRequest, uses a readonly, preallocated buffer that cannot be reinitialized. This caused issues for WebSocket signals (handled by PodeSignalRequest) where a fresh buffer is needed per Receive call.

Changes Introduced:

1. Lazy Buffer Initialization in PodeRequest:

   • Removed the immediate allocation of the buffer from the constructor.
   • Introduced lazy initialization of the buffer using a private backing field with a property:

     private byte[] _buffer;
     protected virtual byte[] Buffer
     {
         get
         {
             if (_buffer == null)
             {
                 _buffer = new byte[BufferSize];
             }
             return _buffer;
         }
     }

   • Added a virtual method GetBuffer() that returns the buffer. By default, it returns the lazily initialized, single preallocated buffer:

     protected virtual byte[] GetBuffer() => Buffer;

2. Override in PodeSignalRequest:

   • In PodeSignalRequest, override GetBuffer() to return a new byte array for each Receive call:

     protected override byte[] GetBuffer() => new byte[BufferSize];

   This ensures that every WebSocket signal request gets a fresh buffer, avoiding any leftover data from previous operations.

3. Integration Test:

   • Added a Pester integration test that creates a WebSocket client to send a JSON signal and asserts that the returned message (e.g. a date string) is correctly received. This test mimics the client behavior from our JS code and ensures that the buffer management in PodeSignalRequest is working correctly.

Impact:

• These changes improve memory management by only allocating the shared buffer when necessary for most requests.
• For WebSocket signals, a new buffer is used on each receive call, ensuring data integrity.
• The modifications are backward-compatible for other request types (e.g., HTTP requests) that benefit from reusing the preallocated buffer.

Testing:

• Verified the changes locally using the provided Pester integration test.
• The WebSocket client test successfully sends a signal and receives the correct response without any buffer contamination issues.

[mdaneri]

Added a note to the documentation regarding the current limit of 32KB payload

[Badgerati]

LGTM