Very similar to password resets and registration, the components pass around a server config for usage by other components. Login is a bit more complicated and needs a few more changes to pull the logic out to a more generic layer.
As part of adding validation to Field, the logic is simpler to follow if we can
assume that all usages of Field use it as a controlled component, instead of
supporting both controlled and uncontrolled.
This converts the uncontrolled usages to controlled.
As with other auth flows, this converts inputs on the login page to use the
Field component for consistent styling. The login type dropdown is left as-is
for now.
Now that auth flows can show a server name like `example.com` which might
delegate the HS to some other server, it could be confusing to see text like
"Sign in to example.com", especially if `example.com` runs an identity service,
uses SSO, has its own account system, or other things like this.
To clarify that we mean Matrix accounts, all auth flows are updated to talk in
terms of "<verb> your Matrix account on <server>".
Fixes part of
https://github.com/vector-im/riot-web/issues/8763#issuecomment-464823909.
If a default server name is set and the current HS URL is the default HS URL,
we'll display that name in the "sign in to" text on the login form.
This can be a bit more user friendly, especially when the HS is delegated to
somewhere such as Modular, since you'll then see "example.com" instead of
"example.modular.im", which you have no direct relationship with as a user.
This is the key bit of https://github.com/vector-im/riot-web/issues/8763 for
login.
