Add subgroups + custom group tags

[johnsusek]

• What kind of change does this PR introduce?
  • A feature to add a subgroup within a group
  • A feature to specify group tag per group

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  No, feature addition only.

• Other information:
  Please see Add subgroups documentation vue-form-generator-docs#28 for documentation

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I've also added subgroups to the dev group example:

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Since these changes allow custom tags and subgroups, complex behavior like putting subgroups into tabs is possible. Here's what it looks like with bootstrap-vue tabs for subgroups:

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Please let me know if there's anything you would like done differently! I hope we can get this subgrouping behavior in, we are using vfg in a project with very complex forms and could really use something like this.

Related issue: #285

[coveralls]

Coverage remained the same at 89.979% when pulling 9bbb143 on johnsusek:feature/subgroups into 721a4ee on vue-generators:master.

[DelfsEngineering]

This is interesting but I think a visible key really needs to be part of this to make it really useful. I think a visible tag in on another PR.
I don't see a sample of what the schema would look like, I am assuming it can go multiple levels deep?

[johnsusek]

For our use case, this functionality is definitely useful and would go into use right away to group forms into subsections. And other people would like it too imho, as evidence I would point to #285.

But maybe I don't understand - can you elaborate on this "visible" feature and why it is important for this PR?

Thanks for the feedback!

[DelfsEngineering]

A visible key at the group level to hide the entire group, currently it must be done via css.

[johnsusek]

That sounds like it would be a useful addition to vfg. If that feature is added to the codebase I would be happy to help integrate it with this subgroups feature.

[DelfsEngineering]

Basically it would allow you to have a login, password reset and sign up groups all in one form.

[DelfsEngineering]

@johnsusek Would this support recursive groups also? or just one level down?

[Mohammad-Alavi]

This is a nice feature. Why it is not merged yet? 🤔

[vortechron]

@icebob merge it please :(