Add API Key authentification method

[richfab]

Some private feeds require an API Key to be fetched.
It would be useful to add the API Key authentification method to validate such feeds.

Before	After

[testower]

What exactly does «API Key» mean in this context?

[richfab]

What exactly does «API Key» mean in this context?

I was thinking API Key in the context of a unique identifier used to authenticate the client to the server. The API Key is passed in the request header, such as X-API-KEY: key. Thoughts?

[testower]

I think the header name should be configurable, since “x-api-key” is non-standard, and it may vary what people use in the field.

[richfab]

I think the header name should be configurable, since “x-api-key” is non-standard, and it may vary what people use in the field.

Good point. I made the header name configurable. Thank you!