API Domain: chaining requests

[mildwonkey]

Description

The API domain’s current functionality supports basic Get and Post API operations. These are insufficient to support common API operations. Even basic API operations may require multiple API calls: some examples include logging in to get an API token, listing all resources before acting on individual resources, and getting IDs from resource names. And even if the API plays nicely with Lula’s current functionality, many validations require more than a single call, and users frequently may need to mutate one API call output for another's input.

Additional Context

While we can solve the API Chaining request today, limitations in Lula’s architecture and configuration language are increasingly holding us back from the most performant and effective solutions. This is therefore a two pronged proposal: implement an experimental API Chaining feature, then tackle the larger  Configuration language/DSL refactor so that we can continue to build on the API chaining (and everything else which will benefit). The actual Configuration Language refactor will be a separate (future) proposal.

1. Implement API Request chaining using the simplest and quickest implementation (that still meets our needs and quality/security requirements)
2. Follow this up by refactoring Lula to use a fully featured configuration language & DSL which will address the various limitations of the selected API chaining solution.