Database traits feature checks

[KyGost]

Perhaps it would make sense to have feature checks?
For example:
Index:

fn supports_index() -> bool {
  // Default:
  false
}

Which then allows one to check and fail early, and more easily print a nicer incompatibility warning.

[KyGost]

Perhaps also info like DBFull::DB_TYPE which gives something like Sled and can be used to print messages like:

if !db.INDEXING {
  Err(format!("Indexing is not supported by {db.DB_TYPE}"))
}