Support required flag for group items

[Supereg]

Problem

Currently, the required flag of group questionnaire items cannot be changed using the survey builder.

We use it now in ResearchKitOnFHIR to render the skip button of a Form step. This exposes useful behavior like requiring at least one answer to several optional questions (e.g., group is set to required and all questionnaire items are not required.

Solution

Support a similar toggle as it is already present with e.g. regular text questions.

Additional context

No response

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