Provide an API endpoint that returns all patterns covering a given address

[nielstron]

This adds the endpoint /v1/patterns/{pattern-frac}
It returns all patterns that completely cover {pattern-frac} (i.e. if the result is non-empty, the user can be sure that {pattern-frac} UTxOs are correctly represented in the DB - this excludes the possibility of dynamically added patterns)

TODO:

• add endpoint
• add documentation

Fixes #40 and #38 (?)

Possible alternatives:

• reduce output to true/false depending on whether the list is non-empty or not
  • pro: reduces size of output
  • thoughts: we have the information anyways, why not expose it? Also, odds are that the output of this function will never be critically large
• reduce input to only single addresses
  • pro: simplifies logic
  • con: reduces usability, especially considering that the user could also query {pattern-frac} and might be concerned about its completeness

[KtorZ]

Thanks for the idea and the contribution.

I can help with the documentation / specifications updates. We'll also need to cover the new additions with unit & property tests when applicable.