Allow to save default config

[dyaskur]

Related to issue #13, it's essential to implement the saving of default configurations.

Currently, the default poll configurations are as follows:

Is anonymous (default: false)
Is allowed to add options (default: true)
Is allowed to close (default: allowed for the creator)
These defaults are hardcoded, and it's crucial to enable the ability to save default configurations on a per-chat space basis.

This implementation may require a change in the Terms of Service (TOS) because it needs a new storage mechanism to store the default configurations. As of now, the app doesn't store any data in our database. The database itself is within chat messages, which are not visible to us.