fix: edge case on context value where trim is not a function

[nunogois]

https://linear.app/unleash/issue/2-2468/fix-trim-is-not-a-function-edge-case-on-context-value

Fixes: Unleash/unleash-proxy#185

This PR addresses the issue reported by @nicks, where a version.trim is not a function error is thrown under certain conditions.

The error occurs when a context value has a custom .toString() method that does not return a string. This was the only scenario in which we could reproduce the issue. A corresponding test has been added to validate this.

The solution suggested by @nicks has been implemented. Specifically, the !isStrictSemver(contextValue) check has been moved inside the try/catch block. This change ensures that any exceptions thrown by this method will be caught, in which case the function will default to false.

A more robust implementation of resolveContextValue has been introduced, which would also prevent the issue. See:

Lastly, we noticed the test files strategy-test.ts and flexible-rollout-test.ts were being ignored in test runs due to their filename format. Renaming them to strategy.test.ts and flexible-rollout.test.ts ensures they are included in the tests as intended.

[coveralls]

coverage: 90.635% (+0.2%) from 90.456%
when pulling 28a584a on fix-context-edge-case-trim-not-a-function
into e61e55a on main.

[chriswk]

Nice. Strange corner case.