feat(common): add log filtering function

[y-nk]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Other... Please describe:

What is the current behavior?

log levels can be passed manually

Issue Number: 14788

What is the new behavior?

a function which helps to smartly parse log level based on string (ideally, env var)

Does this PR introduce a breaking change?

• Yes
• No

Other informations

Since issue was not yet seen, I'll wait for feedback before providing docs, but as you can see in the original issue, doc-friendly explanation was already provided.

[kamilmysliwiec]

CI checks fail

[y-nk]

@kamilmysliwiec my bad, i wrongly assumed jest as test framework.

[coveralls]

Pull Request Test Coverage Report for Build df357106-a247-4cfe-8915-fcd200a8ab37

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 89.292%

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Totals
Change from base Build 44c104f1-8e85-45d8-85b0-095b2f828590:	0.0%
Covered Lines:	7146
Relevant Lines:	8003

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💛 - Coveralls