VaultChangeWatcher - IConfiguration retains deleted keys (removals not applied)

[k0st1x]

Describe the bug

We use Vault as a password manager. When an entry is removed from the Vault file, the change watcher reloads, but the removed key remains in IConfiguration instead of being removed.

To Reproduce

Vault-flie:

{
  "Login1": "pwd",
  "Login2": "pwd"
}

Start the application with VaultChangeWatcher enabled (so configuration reloads when the Vault file changes).
Remove the Login2 entry from the Vault file and save.

IConfiguration still contains the key/value for Login2 ("Login2": "pwd") after the reload.

Expected behaviour

The Login2 key should be removed from IConfiguration after the reload.

[MrZoidberg]

resolved by #77