Add filtering capabilities to the API

[marco-c]

At the moment, the APIs are all retrieving the overall coverage.
We should add filtering capabilities so the frontend can require specific things from the backend.

Filters we should support:

• Platform (Linux, Windows, Mac, etc.);
• Test suite;
• Language?;
• Third-party code?

[jarkyll]

@marco-c Would it be possible to take this on as my first bug?

[marco-c]

There are other bugs that might be more suitable as first good bugs, look for issues with the "skill:good-first-bug" label: https://github.com/mozilla/release-services/issues?q=is%3Aissue+is%3Aopen+label%3Askill%3Agood-first-bug.

[Utkarsh1308]

Can you guide me on what to do here?

[marco-c]

@Utkarsh1308 I suggest picking up a bug with the good first issue tag, this one is a little complicated for a first contibution.

[La0]

@marco-c Are we doing the language & 3rd party filters ?

[marco-c]

These could be generated by the backend on-the-fly when requested. I'd file a separate issue for that.

[marco-c]

Opened #164.