Test coverage for POST projects/task-split endpoint

[azharcodeit]

What type of PR is this? (check all applicable)

• 🍕 Feature
• 🐛 Bug Fix
• 📝 Documentation
• 🧑‍💻 Refactor
• ✅ Test
• 🤖 Build or CI
• ❓ Other (please specify)

Related Issue

Related to Issue #1613

Describe this PR

Added a test for splitting a task into subtasks with POST /projects/task-split endpoint.
Organisation fixture have been refactored to avoid duplication.

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Alternative Approaches Considered

Did you attempt any other approaches that are not documented in code?

Review Guide

Command to run all tests defined in the project using pytest:

docker compose run --rm api pytest

Checklist before requesting a review

• 📖 Read the FMTM Contributing Guide: https://github.com/hotosm/fmtm/blob/main/CONTRIBUTING.md
• 📖 Read the HOT Code of Conduct: https://docs.hotosm.org/code-of-conduct
• 👷‍♀️ Create small PRs. In most cases, this will be possible.
• ✅ Provide tests for your changes.
• 📝 Use descriptive commit messages.
• 📗 Update any related documentation and include any relevant screenshots.

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[spwoodcock]

Nice testing for the 422 too 🙌