Our Composer dependencies are all optional at the moment - Sentry is
only used in the live config file, and we stopped using Google's PHP API
because it was too buggy (we're calling out to Node instead).
(This also removes composer.lock; lockfiles are really unnecessary for
PS's use-case.)
This doesn't support setting accounts up for Google login: that still
has to be manually done via the database by setting the email field to
`username@gmail.com@`, where the second `@` denotes that it's using
Gmail login.
If the email field does end in `@`, `getassertion` will note this by
sending `;;@gmail`, to convey that the server is expecting a Google
login token rather than a password.
Upon receiving `;;@gmail`, the client will replace the password box will
with a Google login button, and then send the resulting Google login
token to the server in the `password` field. The server will validate
the "password" using the Google server libraries, and otherwise handle
the login as normal.
Note that Google login requires various features that a paranoid person
might disable; most notably 3rd-party cookies.
FixesZarel/Pokemon-Showdown#3394
