feat: allow numeric values as CacheContextKey

[Laurens-makel]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: CONTRIBUTING.md#commit
• 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?

allow numeric values as CacheContextKey

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

What is the current behavior?

Issue Number: closes #100

What is the new behavior?

Does this PR introduce a breaking change?

[ ] Yes
[X] No

Other information

Is there any possibility to backport this to the 3.1.x version?

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