Snackbar: Fix type class not taking into account per-snackbar options

[danielchalmers]

Description

Fixes #5027.

var options = new SnackbarOptions(severity, Configuration);
configure?.Invoke(options);

SnackbarTypeClass was set in the SnackbarOptions constructor before the snackbar's configuration was assigned, thus falling back to the global configuration. Now the class creation is handled in SnackBarMessageState.SnackbarClass and SnackbarTypeClass is kept pure.

Docs were updated to reflect this new opportunity.

Note: SnackbarTypeClass can now be null but it's only used in one place (internally) inside a string.

How Has This Been Tested?

visually

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

Checklist:

• The PR is submitted to the correct branch (dev).
• My code follows the code style of this project.
• I've added relevant tests.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 89.08%. Comparing base (222b8bb) to head (e2a37a9).
Report is 28 commits behind head on dev.

Files	Patch %	Lines
...Blazor/Components/Snackbar/SnackBarMessageState.cs	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev    #8423      +/-   ##
==========================================
+ Coverage   88.80%   89.08%   +0.27%     
==========================================
  Files         414      411       -3     
  Lines       12294    12184     -110     
  Branches     2455     2433      -22     
==========================================
- Hits        10918    10854      -64     
+ Misses        844      796      -48     
- Partials      532      534       +2     

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[ScarletKuro]

Thanks.