Connection flatten functions to return diagnostics slice instead of error (2/3)

[willvedd]

Description

Small refactor of the connection resource's flatten functions to return diag.Diagnostics instead of a regular error. What this does is allow more specific diagnostic logging to exist alongside the domain-specific code. Otherwise, we would need to maintain some type of mapping between a custom error type and the diagnostic logs within the higher-level flatten function. This unlock is demonstrated in this PR: #241 .

Checklist

Note: Checklist required to be completed before a PR is considered to be reviewable.

Auth0 Code of Conduct

• I have read and agreed to the terms within the Auth0 Code of Conduct

Auth0 General Contribution Guidelines

• I have read the Auth0 General Contribution Guidelines

Changes include test coverage?

• Yes
• Not needed

Does the description provide the correct amount of context?

• Yes, the description provides enough context for the reviewer to understand what these changes accomplish

Have you updated the documentation?

• Yes, I've updated the appropriate docs
• Not needed

Is this code ready for production?

• Yes, all code changes are intentional and no debugging calls are left over

[willvedd]

I always wondered why we didn't unit test the flatten function because there is quite a bit of logic and complexity wrapped up in them. However, this test is just asserting the simple case of a nil options struct which should return nil.

[willvedd]

This file will also serve as the holding place to test the existence of specific diagnostic information like warnings.

[codecov-commenter]

Codecov Report

Merging #240 (da61912) into main (55081cb) will increase coverage by 0.02%.
The diff coverage is 62.50%.

@@            Coverage Diff             @@
##             main     #240      +/-   ##
==========================================
+ Coverage   82.64%   82.67%   +0.02%     
==========================================
  Files          36       36              
  Lines        6850     6861      +11     
==========================================
+ Hits         5661     5672      +11     
  Misses        938      938              
  Partials      251      251              

Impacted Files	Coverage Δ
auth0/resource_auth0_connection.go	71.33% <33.33%> (ø)
auth0/structure_auth0_connection.go	84.10% <63.76%> (+0.18%)	⬆️

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