Change a few delegate properties in Signup to be weak references

[crazytonyli]

Relates to #21050.

This PR changed a few delegate properties' declaration. I'll post PR comments in detail regarding those individual changes.

Regression Notes

1. Potential unintended areas of impact
   None.

2. What I did to test those areas of impact (or what existing automated tests I relied on)
   None.

3. What automated tests I added (or what prevented me from doing so)
   None.

PR submission checklist:

• I have completed the Regression Notes.
• I have considered adding unit tests for my changes.
• I have considered adding accessibility improvements for my changes.
• I have considered if this change warrants user-facing release notes and have added them to RELEASE-NOTES.txt if necessary.

UI Changes testing checklist: N/A

[crazytonyli]

There is a retain cycle between the SignupEpilogueTableViewController and this SignupEpilogueCell.

WordPress-iOS/WordPress/Classes/ViewRelated/NUX/SignupEpilogueTableViewController.swift

Line 214 in 48b8a39

cell.delegate = self

[crazytonyli]

WordPress-iOS/WordPress/Classes/ViewRelated/NUX/SignupEpilogueViewController.swift

Lines 71 to 79 in 48b8a39

	override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
	super.prepare(for: segue, sender: sender)
	if let vc = segue.destination as? SignupEpilogueTableViewController {
	vc.credentials = credentials
	vc.socialService = socialService
	vc.dataSource = self
	vc.delegate = self
	}

I'm not sure if a view controller would hold strong references to segue instances, which would cause a retain cycle in our case here. But considering how this delegate and dataSource are used, they should be weak references anyways.

[staskus]

Yes, I jumped on this memory leak in other investigations.

[crazytonyli]

This delegate is used in a similar way as #21064 (comment)

WordPress-iOS/WordPress/Classes/ViewRelated/NUX/SignupEpilogueViewController.swift

Lines 80 to 88 in 48b8a39

	if let vc = segue.destination as? SignupUsernameViewController {
	vc.currentUsername = updatedUsername ?? epilogueUserInfo?.username
	vc.displayName = updatedDisplayName ?? epilogueUserInfo?.fullName
	vc.delegate = self
	// Empty Back Button
	navigationItem.backBarButtonItem = UIBarButtonItem(title: String(), style: .plain, target: nil, action: nil)
	}
	}

[crazytonyli]

There is a retain cycle between SignupUsernameViewController and SignupUsernameTableViewController.

WordPress-iOS/WordPress/Classes/ViewRelated/NUX/SignupUsernameViewController.swift

Lines 31 to 36 in 48b8a39

	if let vc = segue.destination as? SignupUsernameTableViewController {
	usernamesTableViewController = vc
	vc.delegate = self
	vc.displayName = displayName
	vc.currentUsername = currentUsername
	}

[wpmobilebot]

📲 You can test the changes from this Pull Request in WordPress Alpha by scanning the QR code below to install the corresponding build.

	App Name	WordPress Alpha
	Configuration	Release-Alpha
	Build Number	pr21064-a530793
	Version	22.7
	Bundle ID	org.wordpress.alpha
	Commit	a530793
	App Center Build	WPiOS - One-Offs #6308

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[wpmobilebot]

📲 You can test the changes from this Pull Request in Jetpack Alpha by scanning the QR code below to install the corresponding build.

	App Name	Jetpack Alpha
	Configuration	Release-Alpha
	Build Number	pr21064-a530793
	Version	22.7
	Bundle ID	com.jetpack.alpha
	Commit	a530793
	App Center Build	jetpack-installable-builds #5331

Automatticians: You can use our internal self-serve MC tool to give yourself access to App Center if needed.

[staskus]

👍 LGTM