Adding the Sign In mutation - requires an extra conditional

[hazartilirot]

Just a little note,
before interrogating a database to check if there is a user with a specific email, we need to validate an email itself. One might disagree with me though I think there is no point in making an unnecessary request to a database if a user sends typical text instead of johndoe@example.com. On one hand it might be unarguably done in the front-end side on the other we shouldn't rely on it.