Simplify subscription clip rules in the Subscriptions API SDK

[asonnenschein]

This PR is intended for v3.0.0; it includes changes that will break v2.0.0. See #1162 for context.

Claude generated PR notes:

Summary of Changes

Problem Solved: Simplified subscription clip rules in the Subscriptions API SDK by removing the confusing dual code paths for clip functionality.

Changes Made:

1. Removed clip_tool() method from planet/subscription_request.py (lines 641-673) - This method is no longer needed since custom clip AOIs are not supported in
   subscriptions.
2. Simplified clip_to_source logic in build_request() method:
   - Changed from copying the source geometry ('aoi': source['parameters']['geometry']) to using empty parameters ('parameters': {})
   - This aligns with the API service contract where empty parameters automatically clip to subscription source geometry
3. Updated documentation:
   - Updated docstring for clip_to_source parameter to reflect the simplified behavior
   - Updated SDK guide documentation to remove references to clip_tool() and mention that custom clip AOIs are no longer supported
4. Updated tests:
   - Modified test expectations to check for empty parameters in clip tool configuration
   - Removed tests for the clip_tool() function
   - All existing tests continue to pass, ensuring backward compatibility for the clip_to_source functionality

API Impact:

• The clip_to_source=True behavior remains unchanged from a user perspective
• The clip_tool() method has been removed (breaking change, but appropriate for a 3.0.0 release)
• Custom clip AOIs are no longer supported, simplifying the API

The implementation now has a single, clear code path for clipping: use clip_to_source=True to clip to the subscription source geometry, or clip_to_source=False
(default) for no clipping. This eliminates the previous confusion between clip_tool() and clip_to_source parameters.

[Copilot]

Pull Request Overview

This PR simplifies the subscription clip rules in the Subscriptions API SDK by removing support for custom clip AOIs and streamlining the clip-to-source functionality. The changes eliminate confusing dual code paths while maintaining backward compatibility for the clip_to_source=True behavior.

• Removed the clip_tool() method since custom clip AOIs are no longer supported
• Simplified clip-to-source implementation to use empty parameters instead of copying source geometry
• Updated documentation and tests to reflect the streamlined API

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
planet/subscription_request.py	Removed clip_tool() method and simplified clip-to-source logic to use empty parameters
tests/unit/test_subscription_request.py	Updated test expectations for empty clip parameters and removed clip_tool tests
docs/python/sdk-guide.md	Updated documentation to remove references to custom clip AOIs

[asonnenschein]

Add note about breaking change to the 3.0 migration guide.

[asonnenschein]

Added bullet point about the v2 -> v3 breaking change in #1173.