Function createLegacyMessagesProvider

createLegacyMessagesProvider(deps: ProviderDeps): MessagingProvider
The legacy provider: the original direct-message format, readable by the widest range of apps but exposing who talks to whom. Specified by NIP-04.
Parameters
- deps: ProviderDeps
  Backend constructor and availability check supplied by the shell.
Returns MessagingProvider
A MessagingProvider with id legacy.
Example
```
registry.register(createLegacyMessagesProvider({
  createBackend: () => nip04Adapter,
  available: () => ({ available: true }),
}));
```