API Gateway: Clean up Tasks

[afsalthaj]

• Make sure we don't have concerning clones in the hot path of a custom http api requests. Please look through the workflow and see if there is any.
• Remove type parameterized ApiDefinition, as the code is pretty much handling only Http now. The early type parameterisation did work out well, however, it was hard for a new contributor to see through these and easily gets into a state of "mixed" approach where, some parts are tightly coupled to Http. Let's be consistent instead of keeping a code that may become reasonable only in future. This is actually a minor change and doesn't sound as complicated.
• Lookup logic for API definition shouldn't rely on Postgres. I think the cache was removed when moving from redis to Postgres. While fixing this point, it's a good idea to see how this is missed out.
• Cors middleware is overly geared to browser's preflight requests. Origin handling should be done at the middleware but currently I see only the out middleware for CORS to add CORS headers, and not 1 for incoming requests (which I think, missed out when lifting and shifting of code and definitely points to absence of a particular test) - A pattern match process_in_middleware for cors is a Noop, which is wrong