Support sending and retrieving caching headers in requests/responses

[johnjohndoe]

Context

• This breaking change allows to set the HTTP headers If-None-Match and If-Modified-Since at a request and get the HTTP headers ETag and Last-Modified from a response. This allows to reduce the transferred data to a minimum due to the support of HTTP 304 Not Modified.

Description

• Let EngelsystemService#getShifts return Response<List<Shift>>.
  • Add eTag and lastModifiedAt parameters.
  • Expose retrofit2.Response in library API.
• Refine Api in general.
  • Rename ApiModule to Api.
  • Change Api#provideEngelsystemService parameter from okHttpClient: OkHttpClient to callFactory: Call.Factory.
  • Require baseUrl parameter in Api#provideEngelsystemService not to be empty string.

Related

• Make raw response accessible to distinguish between cache or server response. #13

[github-actions]

Test Results

14 tests  ±0   14 ✅ ±0   2s ⏱️ ±0s
 5 suites ±0    0 💤 ±0 
 5 files   ±0    0 ❌ ±0 

Results for commit 47e5297. ± Comparison against base commit 99af090.

This pull request removes 2 and adds 2 tests. Note that renamed tests count towards both.

info.metadude.kotlin.library.engelsystem.ProductionApiTest ‑ Validates a failure shifts response()
info.metadude.kotlin.library.engelsystem.ProductionApiTest ‑ Validates a successful shifts response()

info.metadude.kotlin.library.engelsystem.ProductionApiTest ‑ getShifts responds successfully()
info.metadude.kotlin.library.engelsystem.ProductionApiTest ‑ getShifts throws HTTP exception()