class Async::HTTP::Protocol::HTTP2::Stream

def add_header(key, value, trailer: false)

@parameter value [String] The header value.
@parameter key [String] The header name.
Add a header to the stream, validating against HTTP/2 constraints. 
def add_header(key, value, trailer: false)
	if key == CONNECTION
		raise ::Protocol::HTTP2::HeaderError, "Connection header is not allowed!"
	elsif key.start_with? ":"
		raise ::Protocol::HTTP2::HeaderError, "Invalid pseudo-header #{key}!"
	elsif key =~ /[A-Z]/
		raise ::Protocol::HTTP2::HeaderError, "Invalid upper-case characters in header #{key}!"
	else
		@headers.add(key, value, trailer: trailer)
	end
end