Create Requests for Training

[wladyDE]

If I want to join the training, I must click the join button, and then I send a request to the creator of the training. They will see in their requests that a new request has appeared, and they will be able to either accept or reject my request.
After acceptance, I will be added to the participants, and when viewing the training, there will be one more participant. Later on, it will be possible to see profile photos and information about the participants.

Something like this:

[wladyDE]

Now, to join a workout, you first need to press the "Join" button and send a request to another user. They will instantly receive a notification and can either accept or decline your request. Upon acceptance, the number of participants will increase by one. In the future, we will implement the ability to see who is participating in the workout right away (name, surname, photo), and also enable a chat with the creator of the workout. If your request is declined, you won't be able to apply for the same workout again.

For now, I've focused on the logic. We'll completely refine the design when we implement several other features.

[wladyDE]