Add support for API keys as an authentication scheme

[Badgerati]

Add support for a new authentication scheme: -ApiKey.

This should allow for an API key to be supplied in either a Header, Cookie, or Query string (-Location), and the name of the property should be settable (-LocationName - potentially no default).

This will also need testing via Swagger, to make sure the output is correct.

For example, to get an API key from an X-API-KEY header:

New-PodeAuthScheme -ApiKey -Location Header -LocationName 'X-API-KEY' | Add-PodeAuth -Name 'Example' -Sessionless -ScriptBlock {
    param($key)
}

Or, to get an app_id key from query string:

New-PodeAuthScheme -ApiKey -Location Query -LocationName 'app_id' | Add-PodeAuth -Name 'Example' -Sessionless -ScriptBlock {
    param($key)
}

If the Header/Query/Cookie is missing, or if the value is empty, then a 401 HTTP response should be returned. Otherwise, no further validation and the key should be supplied to the Add-PodeAuth scriptblock.