Fix #1649 Extending Onboarding UI Below Safe Area

[chickdan]

Summary of Changes

This change sets the bottom of the modal equal to the superview and provides a new content inset for the description stack view to account for the size of the safe area.

Regarding the centering of the button noted in the issue: I noticed the button is off center on all of the onboarding modals and feel like the change(s) could potentially be large enough to be out of scope.

This pull request fixes issue #1649

Submitter Checklist:

• Unit Tests are updated to cover new or changed functionality
• User-facing strings use NSLocalizableString()

Test Plan:

Screenshots:

Reviewer Checklist:

• Issues include necessary QA labels:
  • QA/(Yes|No)
  • release-notes/(include|exclude)
  • bug / enhancement
• Necessary security reviews have taken place.
• Adequate unit test coverage exists to prevent regressions.
• Adequate test plan exists for QA to validate (if applicable).
• Issue is assigned to a milestone (should happen at merge time).

[Brandon-T]

We shouldn't hardcode the safe-area inset. See below comment :)

[Brandon-T]

This would change to:

mainStackView.snp.makeConstraints {
    $0.leading.trailing.bottom.equalToSuperview()
}

[Brandon-T]

and this would change to:

descriptionStackView.snp.makeConstraints {
    $0.edges.equalTo(descriptionView.safeArea.edges).inset(UX.descriptionContentInset)
}

Now you don't have to worry about "52" :). It will automatically calculate how far from the bottom it should be.

[Brandon-T]

For this particular ticket, when we change it to extend the safe-area insets, we also have to update the animation in OnboardingNavigationController line: 244

[iccub]

This will get fixed in #1684, sorry for that.

Brandon assigned himself to this task few days ago, for contributors it's usually the best to take tasks without assignments or ask if it can be picked up in case someones is assigned to it.

Really appreciate your help, your first PR #1628 should get merged in after one more round of code review :)