[MINT-3211] Custom Solutions Form Modal

[garyjzhao]

MINT-3211

Description

• Add MTOMilestoneTranslation and all the CH stuff
• Add SolutionForm component, testing file, gql mutation, translations

How to test this change

1. Navigate to MTO home page
2. Click Add custom solution button
3. Verify that modal matches figma and functions as expected
4. Verify error and success messages

PR Author Checklist

• I have provided a detailed description of the changes in this PR.
• I have provided clear instructions on how to test the changes in this PR.
• I have updated tests or written new tests as appropriate in this PR.
• Updated the Postman Collection if necessary.

PR Reviewer Guidelines

• It's best to pull the branch locally and test it, rather than just looking at the code online!
• When approving a PR, provide a reason why you're approving it
  • e.g. "Approving because I tested it locally and all functionality works as expected"
  • e.g. "Approving because the change is simple and matches the Figma design"
• Don't be afraid to leave comments or ask questions, especially if you don't understand why something was done! (This is often a great time to suggest code comments or documentation updates)
• Check that all code is adequately covered by tests - if it isn't feel free to suggest the addition of tests.

[patrickseguraoddball]

LG, nice Gary :)