Const added to members, chunked trailer support to HTTP/1, HTTP2 headers

HTTP2 headers

• pseudo headers are pushed into the front of the array list, and other than that, it will be treated the same as normal headers
• Trade off:
  • We know that push front to the array list is expensive. But, it should be used only few times, as you don't want to change pseudo headers a lot and there are at most 4 of them. More than that, we don't need to do the push front later when we need to send the headers into the wire.
  • The advantage of it is that we will have the mostly the same behavior as netty, which is used by Java SDK team already.
• add will push the pseudo header to the front of the list when needed (the last header is NOT pseudo header)

Chunked trailer

• Add chunked trailer support to HTTP/1

Const changes

• const added to aws_socket_options
• const added to aws_http_proxy_options
• const added to aws_tls_connection_options

Removed OOM conditions/tests

removed OOM test, since that's no longer allowed, (#343)

* removed OOM test, since that's no longer allowed,

BYO_CRYPTO fix and proxy environment variable fix

v0.6.7

BYO_CRYPTO test and fix (#337)

Proxy environment variable support

• Proxy environment variable support HTTP_PROXY and HTTPS_PROXY
• When enabled:
  • env HTTPS_PROXY/https_proxy will be checked when the main connection use tls.
  • env HTTP_PROXY/http_proxy will be checked when the main connection NOT use tls.
  • The lower case version has precedence.
• Metrics exposure
• Http2 on going supports

Address GCC11 warnings

v0.6.5

Fix GCC11 warnings (#326)

More validation of HTTP/1.1 messages

More validation of HTTP/1.1 messages. (#321)

Add validation for the following, according to the ABNF defined in RFC-7230.
- header field-names
- header field-values
- request method
- request-path aka URI
- response reason-phrase

Previously, we did an OK job validating incoming messages, but did no validation whatsoever of outgoing messages.

Caveats:
- URI validation is extremely basic for now.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

Http proxy socket channel support

• Adds a new API for creating a socket channel through an http proxy, allowing for arbitrary protocols to establish a connection through such a proxy

Proxy refactor

• Significant refactor of proxy support, including
• • Tunneling vs. forwarding is an explicit configuration choice, and no longer implicit based on tls properties. The behavior of existing applications should remain unchanged.
• • Implemented a new proxy "strategy" system for authentication. Strategies exist for no authentication, basic authentication, and synchronous strategies are now in place to support kerberos and ntlm authentication. Strategies can be linked together in a chain and attempted sequentially. Existing authentication controls remain in place but are deprecated and now map to the new strategy types.

Timeout the integration test

• Add timeout for our integration test about http

New managed thread API

Convert to new managed thread system for threads that cannot be reliably explicitly joined.