Error handlingv2

[wmcginty]

This should help address #28 .

Changes made:

• Created a new protocol, NetworkServiceFailureInitializable (not sold on the name). This is any error that can be initialized from a NetworkServiceFailure as so: init(networkServiceFailure:)
• Created a new protocol, DecodingFailureInitializable (not sold on the name). This is any error that can be initialized from a failed Codable decode as so: init(decodingError:data:).
• Removed BackendServiceError. It is now only implemented in tests.
• Created another associated type for NetworkRequest, ErrorType, which must be NetworkServiceFailureInitializable. AnyError has been expanded to conform to this protocol, soAnyNetworkRequest` is unchanged (but lots of code has been deleted, so yay).

This combination of changes allows for a few improvements:

• If the NetworkService creates any sort of failure response, instead of getting a generic BackendServiceError, NetworkRequest.ErrorType.init is called with the reason for the failure. This should give easy access to the Data in the failure (and any other part of it).
• If the NetworkRequest.ResponseType conforms to Codable and fails to decode, NetworkRequest.ErrorType.init can be called with both the failure and the data attempting to be decoded. There is an extension to apply a default for when NetworkRequest.ErrorType conforms to DecodingFailureInitializable.

Oh, and it changes the interface significantly enough that, if approved, we'll want to roll it up with some of the other proposed v2 changes.

[codecov-io]

Codecov Report

Merging #38 into release/2.0.0 will increase coverage by 0.14%. The diff coverage is 88.23%.

@@                Coverage Diff                @@
##           release/2.0.0      #38      +/-   ##
=================================================
+ Coverage          95.67%   95.82%   +0.14%     
=================================================
  Files                 27       26       -1     
  Lines                810      814       +4     
=================================================
+ Hits                 775      780       +5     
+ Misses                35       34       -1

Impacted Files	Coverage Δ
...per/Test Defaults/NetworkRequestTestDefaults.swift	100% <ø> (ø)	:arrow_up:
...space/Service/Network/NetworkServiceProtocol.swift	96.15% <ø> (ø)	:arrow_up:
...erspace/Service/Backend/BackendServiceHelper.swift	100% <100%> (ø)	:arrow_up:
Tests/BackendServiceTests.swift	98.64% <100%> (-0.02%)	:arrow_down:
Sources/Hyperspace/Request/NetworkRequest.swift	100% <100%> (ø)	:arrow_up:
...es/Hyperspace/Service/Backend/BackendService.swift	100% <100%> (ø)	:arrow_up:
Tests/Helper/Mocks/MockBackendService.swift	60% <75%> (+60%)	:arrow_up:

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[wmcginty]

@tylermilner I put a CHANGELOG.md entry together. I can look at creating a migration guide as we get closer to 2.0 release.

[tylermilner]

Looks good. Maybe just merge this into a release branch so that we're not touching master until we're ready to release version 2.0?

[wmcginty]

Switched over to merge back into release. Should be good to go now.