fix: VerifyApiKey config getter and conditions

[stelam]

I've been experimenting with Filestash, particularly its API, and encountered a weird issue: any API key I provided was being accepted.

I suspect the VerifyApiKey() function has been broken for some time:

1. The api_key parameter wasn't utilized within the function. All conditions and comparisons were conducted against the apiKey, sourced from the config.
2. There's a typo in the config path when retrieving the apiKey config value. Consequently, the apiKey value always returns as an empty string. This also means any API key will be accepted if the API_KEY environment variable isn't defined.

Other things (feel free to change):

• I renamed apiKey to allowedApiKeys for clarity
• Added the --legacy-peer-deps flag in the contribution doc, that flag seems to be required (and it's also present in the Dockerfile)

[stelam]

PTAL @mickael-kerjean 🙏

[mickael-kerjean]

thanks!