Preserve user ID casing in state

[willvedd]

Description

As noted in #41 , the Terraform inexplicably converts all user IDs to lower case when writing to state. The specific block of code in question is:

StateFunc: func(s interface{}) string {
   return strings.ToLower(s.(string))
},

This was added in this commit that was pushed directly to master. It doesn't appear that this code serves any functional purpose and I suspect that it was added in error. Additionally, this line is taken from one of the Terraform SDK examples, which further suggests that it doesn't serve a functional purpose to Auth0.

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

[codecov-commenter]

Codecov Report

Merging #197 (bfaa0af) into main (743180c) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #197      +/-   ##
==========================================
- Coverage   83.89%   83.88%   -0.01%     
==========================================
  Files          35       35              
  Lines        6059     6056       -3     
==========================================
- Hits         5083     5080       -3     
  Misses        773      773              
  Partials      203      203              

Impacted Files	Coverage Δ
auth0/resource_auth0_user.go	72.39% <ø> (-0.37%)	⬇️

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[sergiught]

Just as a non-blocking suggestion, it might be worth updating the docs now and specifying that the user_id is now case sensitive.

e.g.

* `user_id` - (Optional) String. ID of the user (case-sensitive).