Add config option CONFIG_CHECK_JSON_LENGTH to check for correct JSON length.
Switch config parameters from defines to enums.
Prefix config variables with CONFIG_
Use CONFIG_ parameters also in tests.
Take out dynamic increase of peer->write_buffer for simplicitiy reasons.
Make write_buffer size check unlikely.
Take out unit test for dynamically increasing peer->write_buffer.
Remove no longer required parameter CONFIG_WRITE_BUFFER_CHUNK.