PAS-556 | Add support for credential hints to the register flow

[Tyrrrz]

Ticket

• Closes https://bitwarden.atlassian.net/browse/PAS-556

Description

This adds an ability to provide credential hints to the /register endpoint.

Shape

Screenshots

Checklist

I did the following to ensure that my changes were tested thoroughly:

• I used the Playground to verify that setting different hints results in different behavior

I did the following to ensure that my changes do not introduce security vulnerabilities:

• __

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 52.38095% with 10 lines in your changes missing coverage. Please review.

Project coverage is 34.84%. Comparing base (4d08754) to head (e64329d). Report is 3 commits behind head on main.

Files	Patch %	Lines
...nConsole/Pages/App/Playground/NewAccount.cshtml.cs	0.00%	9 Missing :warning:
src/Service/TokenService.cs	87.50%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #670 +/- ## ========================================== - Coverage 34.85% 34.84% -0.01% ========================================== Files 565 565 Lines 30945 30961 +16 Branches 923 924 +1 ========================================== + Hits 10785 10788 +3 - Misses 20018 20031 +13 Partials 142 142 ```

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