fix: expand typescript support to null when allowNull is true

[arthurpankiewicz]

Description

• when an attribute is not required (allowNull) then the coerce function does not allow undefined, but the frontend was only supporting <type> | undefined with typescript
• expanded typescript to be <type> | null | undefined
  • even though undefined will throw an error in coerce function, it is required so that the field can be omitted entirely, ie. createOne({ name: undefined }) will throw an error, but omitting the attribute entirely createOne({}) works. TS cannot tell the difference between these 2

Test Plan

• manually tested

Definition of done

• Does new code have 90% testing coverage (100% for core) of both unit and E2E tests?
• Is code secure? If applicable, add security notes to the description.
• Do all new TODO comments have Jira links with enough information?
• Has the browser error-console been reviewed to not contain new errors introduced by these code changes?
• The site looks “good” above 1000px width.
• The site looks “good” when the window height is small. No double scrollbars.
• Were the changes tested to ensure 508 compliance?