Function defineProvider

defineProvider(
definition: ProviderDefinition,
deps: ProviderDeps,
): MessagingProvider
Join a fixed provider definition with injected shell dependencies.
Parameters
- definition: ProviderDefinition
  Id, copy and security properties.
- deps: ProviderDeps
  Backend constructor and availability check.
Returns MessagingProvider
A MessagingProvider ready for MessagingRegistry.register.
Example
```
const provider = defineProvider(
  { id: 'demo', name: 'Demo', description: 'For previews.', properties },
  { createBackend: () => createMemoryBackend(), available: () => ({ available: true }) },
);
```