Extract UnmockFaker from Backend.

[ksaaskil]

• Extract UnmockFaker class responsible for faking responses to serialized requests, lifting that responsibility from Backend class.
• Refactor unmock.nock so that the same API can be used also from UnmockFaker to add services
• Add helper methods to ServiceStore: update, removeAll, resetServices

The purpose of all this is that one can separate the mock generation logic from the interceptor logic: one can create mock responses via UnmockFaker without starting the interceptor and add new services and modify their states. And it's nice that one can create multiple independent fakers, as the big bad global interceptor is separate from the faking logic.

[codecov-io]

Codecov Report

Merging #355 into dev will decrease coverage by 0.64%. The diff coverage is 77.64%.

@@            Coverage Diff             @@
##              dev     #355      +/-   ##
==========================================
- Coverage   81.06%   80.42%   -0.65%     
==========================================
  Files          53       54       +1     
  Lines        2361     2416      +55     
  Branches      577      586       +9     
==========================================
+ Hits         1914     1943      +29     
- Misses        447      473      +26

Impacted Files	Coverage Δ
packages/unmock-core/src/nock.ts	74.73% <100%> (ø)	:arrow_up:
packages/unmock-core/src/backend/index.ts	89.09% <100%> (-0.2%)	:arrow_down:
packages/unmock-core/src/index.ts	79.24% <66.66%> (-5.76%)	:arrow_down:
packages/unmock-core/src/service/serviceStore.ts	82.53% <73.17%> (-17.47%)	:arrow_down:
packages/unmock-core/src/faker/index.ts	80.76% <80.76%> (ø)
...kages/unmock-node/src/loggers/filesystem-logger.ts	66.66% <0%> (-29.63%)	:arrow_down:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 0298b97...c7215de. Read the comment docs.

[ksaaskil]

Yeah we should add something about it in the documentation! It's currently however more for internal development and it'll likely change quite a bit as new needs emerge, so I wouldn't maybe do that yet.