More EventSub Subscription Types

[DNEAVES]

Pull request summary

Added two additional EventSub subscription types, to match up with regular subscriptions:

Subscription Gifts

• server: EventSubClient.subscribe_channel_subscription_gifts
• models: ChannelSubscriptionGiftData
• models: _SubscriptionTypes.subscription_gift

All needed to enable subscriptions for the gifting of subs. Distinctly different from ChannelSubscribeData with is_gift==True, which is receiving gifted subs.

Subscription Messages

• server: EventSubClient.subscribe_channel_subscription_messages
• models: ChannelSubscriptionMessageData
• models: _SubscriptionTypes.subscription_message

Needed for enabling resubscription messages, and other associated resub data like duration, streak, etc.

Additional

Also created EventSubClient.delete_all_active_subscriptions(), a convenience method for deleting any active EventSubs, in case a user wants to start fresh each time (to avoid duplicate subscriptions).

Checklist

• [x] If code changes were made then they have been tested. (through localhost with Twitch's CLI, not yet through public callback.)
  • [x] I have updated the documentation to reflect the changes.
  • [x] I have updated the changelog with a quick recap of my changes.
• [ ] This PR fixes an issue.
• [x] This PR adds something new (e.g. new method or parameters).
• [ ] This PR is a breaking change (e.g. methods or parameters removed/renamed)
• [ ] This PR is not a code change (e.g. documentation, README, ...)

[DNEAVES]

Changed changelog to be under the "Master" heading. Haven't built the docs, but updated them to point to exactly where they are in the code.

Merged in Master, so should now be up-to-date

[chillymosh]

I just built the docs and they don't link to anything.

[DNEAVES]

Updated changelog again. event_eventsub_notification_.... will now point to their locations in the docs.

EventSubClient.subscribe_channel_subscription_.... will not, since "The above is broken, and does not show members" (referencing EventSubClient). EventSubClient.delete_all_active_subscriptions will not for the same reason.

Fun Fact: Don't add parenthesis in changelogs

[DNEAVES]

Found something (:undoc-members:) that will show EventSubClient members, fixing the "does not show members" thing above. Also fixed the lack of linking for the subscribe_channel_.... functions

[IAmTomahawkx]

In an effort to get this PR into the next release, I've made the requested changes. Thanks for the PR!