Improve redis counter API

[PeeHaa]

Currently the redis counter expects passing in the key.

Is this really needed? I was thinking we could just create the following API instead:

interface Counter {
    public function increment(): Promise;
    public function decrement(): Promise;
    public function get(): Promise;
    public function set(int $val): Promise;
}

This way we don't have to pass in the key as a string.

[PeeHaa]

After discussion we are going to remove the redis dependency entirely and just keep track of users ourselves.

The above mentioned API change will still be needed,

[PeeHaa]

Fixed in https://github.com/ekinhbayar/gitamp/commit/58eb61716b864fab5e45a51016268dc5a72174ab