Get the channelName parameter from the request context and validate it.

Get the videoType parameter from the request context and validate it.

Create a new instance of the YTService interface and return it.

Verify the given videoType parameter is a valid video type by checking if it is in the `ValidVideoTypes` slice.

A slice of valid video types that can be requested from the YouTube API.

The interface for the YouTube service, which is what's used by other modules/files to interact with the YouTube API.