Add Toyhouse OAuth2 authentication

[corowne]

It's here!! Big thank you to TH admin for getting OAuth2 up and working 🙏💖💕

Go to https://toyhou.se/~developer to set up a client and grab your keys.

This setup was a bit more finicky than the others (code-wise), and there are a few things to note while using it:

• This can't be tested from localhost (there might be workarounds but it might still be annoying, I set up an instance on my server to test it)
• When creating a new app, the redirect URL has to be very specifically http://your-site.com/auth/callback/toyhouse as it doesn't seem to use wildcard matching. You may have to enter both non-www and www variants if you use them, etc.

Aside from these, no database/composer updates required. Please add to .env:

TOYHOUSE_CLIENT_ID=
TOYHOUSE_CLIENT_SECRET=

A couple of notes:

• I wrote a custom Socialite provider, but an official one MIGHT be added eventually so I'll change it then.
• Unlike the others, this one uses the Socialite driver stateless - received this recommendation for a stubborn error. It seems to work fine but I'm not entirely sure about the implications of this yet.
• Since TH is widely used within the adoptables community, and with dA sinking like the Titanic, I've opted to make this a primary alias type by default.

On an unrelated note I used the admin account setup to verify/enter an initial deviantART alias, but it still acted like I didn't have an alias attached (redirected me to the link page, and the new alias I authorised got set as a primary alias, so I ended up with 2 primary aliases) so there's probably a bug to look at there.

[itinerare]

Tested and works like a charm!
Noting here that I used all variations of redirect URL (w/ and w/o www, http vs https) in case it makes a difference....