11 req parsing handle chunked encoding

[u413-284-si]

Introduces ability to parse chunked bodies:

Chunked body:

• indicated by "Transfer-Encoding: chunked"
• format:
• chunk size in hex representation and CRLF
• chunk data and CRLF
• read and convert chunk size
• read chunk data and check if chunk size corresponds to actual chunk size
• end of chunked body indicated by zero-size chunk = break condition of loop

Non-chunked body:

• indicated by "Content-Length" (can be overwritten by Transfer-Encoding, then revert to chunked body)
• fix parsing to insert newlines at correct positions while reading the body line by line

Generally fix interpretation of header fields "Transfer-Encoding" and "Content-Length" according to RFC 7230 and RFC 9112.

Add tests for body parsing.

TLDR: Enhance HTTP request parser with ability to read chunked and non-chunked bodies.

close #11