Allow multipolygons to choose as task area

[Sujanadh]

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

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

Related Issue

• Issue Internal server Error trying to create project using multipolygon  #1640

Describe this PR

This PR addresses issue of not supporting multipolygons to upload as a project aoi.
Updates:

• when multipolygons are uploaded as an aoi, those polygons gets dissolved to create a single aoi
• if we want to split task without dissolving those polygons we can pass dissolve_polygon = False since task-splitter can splits those separate polygons
• we can ask for a param (dissolve_polygons = True/False)from user if they want to dissolve those polygons while splitting it (not implemented yet)

Screenshots

Provided in the mentioned issue.

Alternative Approaches Considered

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

Review Guide

Notes for the reviewer. How to test this change?

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.

[optional] What gif best describes this PR or how it makes you feel?

[spwoodcock]

I think having to ask the user overcomplicates it for them.

From the user perspective they just want to upload a geojson and have it work.

If they upload a multipolygon, can we:

• Support dissolving to a single polygon for downloading a data extract (already works).
• Allow the user to Choose area as task, to creates a task from each polygon in the multipolygon.
• Allow the user to Split by square or Splitting algorithm by dissolving the multipolygon into a single polygon.

Do you think this is possible?

[Sujanadh]

I think all the mentioned criteria can be achieved with this PR; dissolving polygon wasn't there incase of disjoint polygons if any, this PR solves it too.
User deciding to dissolve the polygon hasn't been implemented, though I just had a thought about it.
So, this PR is ready to get merged.