Add missing endpoints to the public API: Send Testimonial Request + Create Testimonial Image

Two actions are available in the Senja Zapier integration but absent from the public REST API (api.senja.io/v1):

• Send a Testimonial Request

• Create Testimonial Image

This means these actions are inaccessible on Activepieces, Make, n8n, or any custom integration. Adding them as standard REST endpoints would bring full parity with the Zapier integration and allow any platform to offer the same capabilities.