Add patch method using the PATCH HTTP verb

[jdeniau]

Summary

Adds a patch method to AbstractClient, available on every repository.

It behaves exactly like update (same arguments, same UnitOfWork dirty-field handling — only dirty fields are sent) but issues a PATCH request instead of PUT.

sdk.getRepository('products').patch(entity);

Implementation

• Factored the shared body of update into a private _update(method, …) helper.
• update() delegates to _update('PUT', …), patch() delegates to _update('PATCH', …).

Tests

• allow passing request params in patch — checks request params forwarding and that the PATCH verb is used.
• patching data with unit of work — checks the dirty-diff works with PATCH (only { status: 'foo' } is sent, then {} when nothing changed).

All AbstractClient tests and yarn lint pass.

Note

The content type stays application/json (same as update). If your API expects application/merge-patch+json, pass it via requestParams.headers.