Add method to create Models from only required fields

[PacificBird]

PR Info

Closes #2834. As it stands right now this is very much a draft. I am unable to execute my unit test as running cargo test --workspace fails to compile, although cargo check finds no errors.

To-do:

• Figure out how to get tests to compile
• Clean up the macro implementation
• Workshop the method name
• Discuss if we want to split this up into an optional derive macro on Model instead of being derived by default in ModelEx.

Breaking Changes

• A method model_from_required is added to ModelEx in the respective derive macro.

[tyt2y3]

sorry for the trouble running tests, I've added some instructions in 51dd40b