feat: implement flexible http method mapping

[arielsepton]

PR Description: Add Support for Custom Action-based HTTP Mappings (CREATE, UPDATE, OBSERVE, REMOVE)

Summary

This PR extends the current HTTP method mappings by introducing custom actions: CREATE, UPDATE, OBSERVE, and REMOVE. These actions provide greater flexibility for managing a variety of API interactions while ensuring backward compatibility with existing HTTP methods (GET, POST, PUT, DELETE).

Changes

• Added support for custom actions: CREATE, UPDATE, OBSERVE, and REMOVE in the mappings section.
• These custom actions extend functionality beyond traditional HTTP methods, giving users more control over API workflows.
• Standard HTTP methods (POST, GET, PUT, DELETE) remain fully supported without any changes, preserving compatibility.

Example Usage

Updated documentation with examples demonstrating how to use the new CREATE, UPDATE, OBSERVE, and REMOVE actions.

Motivation

These additional methods offer greater flexibility for users who require more control over complex API interactions, improving the ability to manage workflows and resource states.

Testing

• Unit tests have been added to validate the functionality of the new actions (CREATE, UPDATE, OBSERVE, and REMOVE).
• Integration tests confirm that the feature is backward-compatible and existing mappings remain unaffected.

Notes

This change is fully backward-compatible, ensuring that existing workflows using the traditional HTTP methods continue to function as expected.

Fixes #58

I have:

• Read and followed Crossplane's [contribution process].
• Run make reviewable test to ensure this PR is ready for review.