SqlDatabaseMail: Do not enforce parameters not part of configuration

[johlju]

Pull Request (PR) description

• SqlDatabaseMail
  • Now if a non-mandatory property is not part of the configuration it will
    not be enforced (issue SqlDatabaseMail: Updates properties even if they are not part of the configuration #1661).

The unit tests covers this change. The unit test that is converted for Pester 5 will make the tests more obvious.

This Pull Request (PR) fixes the following issues

• Fixes SqlDatabaseMail: Updates properties even if they are not part of the configuration #1661

Task list

• Added an entry to the change log under the Unreleased section of the
  file CHANGELOG.md. Entry should say what was changed and how that
  affects users (if applicable), and reference the issue being resolved
  (if applicable).
• Resource documentation updated in the resource's README.md.
• Resource parameter descriptions updated in schema.mof.
• Comment-based help updated, including parameter descriptions.
• Localization strings updated.
• Examples updated.
• Unit tests updated. See DSC Community Testing Guidelines.
• Integration tests updated (where possible). See DSC Community Testing Guidelines.
• Code changes adheres to DSC Community Style Guidelines.

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This change is 

[codecov]

Codecov Report

Merging #1662 (45306ec) into master (05b3c8e) will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master   #1662   +/-   ##
======================================
  Coverage      97%     97%           
======================================
  Files          38      38           
  Lines        6256    6256           
======================================
  Hits         6098    6098           
  Misses        158     158           

Flag	Coverage Δ
unit	97% <100%> (ø)

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Impacted Files	Coverage Δ
...urces/DSC_SqlDatabaseMail/DSC_SqlDatabaseMail.psm1	98% <100%> (ø)

[johlju]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @johlju)