Move elastic-apm-http-client into this repository #3506
Description
The mentioned package is meant to be used only by the nodejs APM agent and having it as a dependency it slows down the time to respond to an issue related to it since:
- we need to implement the fix in the package
- we need to publish a new version of it
- we need to update the dependency in the agent (and maybe update its integration code)
- we can finally publish the fixed version
Since a new major release is coming (4.x) the effort will be doubled since we will also keep doing maintenance of 3.x. So for the sake of better maintenance of both versions we should include the sources of the apm-client into the agent. With this approach we will have:
- less steps to publish a fix
- easier backporting of that fix to 3.x
There is already a module inside the agent named apm-client waiting for the code to be included there.