Minimal HTTP login server

[ranisalt]

Pull Request Prelude

• [x] I have followed proper The Forgotten Server code styling.
• [x] I have read and understood the contribution guidelines before making this PR.
• [x] I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

We need to provide a HTTP login server in order to allow connections from recent client versions. HTTP login can (and most likely should) be provided by an AAC that already provides other HTTP services such as a website and an API, but for simple servers we can embed a minimal login server so that a server can be fully started without external tools.

Related work:

• 2010

• 3942 (same as above, but rebased)

• nekiro/OT12LoginServer (external login server in Python)

Opposite to the two linked pull requests, this only provides a minimal login server and players online endpoint. There are no Lua handlers or support for any other routes, which should be responded by the AAC - news, event calendar, and possibly others.

In the future, when boosted creature/boss are implemented, we can also modify the HTTP server to respond to these routes.

This pull request must be merged after #4675 otherwise it is too massive! Merging it as is will also close #4661

[ranisalt]

Somehow I removed the http server when rebasing