feat: make default credentials for auth customizable

[karmingc]

The current implementation defaults to username: admin and password: zwave when enabling auth. However, it can also be beneficial to make this customizable so that it can avoid some additional steps in updating these values.This is completely backwards compatible as well.

@robertsLando I didn't see any contributing guidelines, but if there's anything missing, please let me know.

[coveralls]

Pull Request Test Coverage Report for Build 10922937236

Details

• 2 of 2 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 21.084%

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Totals
Change from base Build 10922544769:	0.0%
Covered Lines:	3924
Relevant Lines:	19787

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💛 - Coveralls