Epic: Create Twitch Configuration Service

[csharpfritz]

As a standalone app service, we should allow TagzApp instances to get the following data from Twitch:

• OAuth access tokens for chatbots
• Profile pictures for Twitch chatters

This will support a dramatically improved Twitch configuration experience for TagzApp in containers and TagzApp as a native application

[csharpfritz]

let's store URLs for Twitch user profile pictures in a Redis cache with 1 hour expiration

[csharpfritz]

Use Implicit Code flow like how the twitch chat password generator page works: https://twitchapps.com/tmi/

We will need to check expiration of access tokens inside of TagzApp and prompt administrators to refresh their credentials when needed