Improvements to collaboration UI

[danilo04]

Fixes #1508

Fix

This PR adds a series of improvements asked in #1508. Those improvements include:

1. Update the Collaborator UI to use a FAB to add new collaborators. This is more consistent with other parts of the UI (e.g. tags)

Empty List	Collaborators List

2. Validate whether the user is trying to add their own email as a collaborator

Test

1. Go to a note
2. Tap on the menu on the top right corner (dot ...)
3. Tap on collaborators
4. Tap on Add Collaborator and type anything that is not a valid email. A message invalid collaborator should be shown.
5. Write a valid email address and tap on Accept. Should update the layout to list of collaborators
6. Tap on the cross icon to remove the collaborator. Should update the layout to show the initial message
7. Tap on Add Collaborator and enter an email address from another valid Simplenote account
8. The note should be shared with the other account
9. Tap on Add Collaborator and enter your account's email. It should show the error message: You cannot add yourself as a collaborator

Review

Only one developer and one designer are required to review these changes, but anyone can perform the review.

Release

These changes do not require release notes.

[peril-automattic]

You can test the changes on this Pull Request by downloading the APK here.

[ParaskP7]

👋 @danilo04 !

I have reviewed and tested this PR as per the instructions, everything works as expected, good job! 🌟

I have left a test related question (❓), a suggestion (💡) and a few minor (🔍) comments for you to consider. I am going to approve this PR anyway, since none is blocking. I am NOT going to merge this PR yet to give you some time to apply any of my suggestions. However, feel free to ignore them and merge the PR yourself.

PS: I was seeing a lot of issues that could have been fixed prior creating a commit if maybe Reformat code, Rearrange code and Optimize imports were enabled. I am also not sure if your AS settings differ from mine. Can we sync on that so I can understand why that is indeed happening and maybe help you out avoiding those in the future?

[danilo04]

Howdy 👋 @ParaskP7. Thanks for the review. Let me address your comments

PS: I was seeing a lot of issues that could have been fixed prior creating a commit if maybe Reformat code, Rearrange code and Optimize imports were enabled.

Definitely, I will enable these options because without it is it a lot of work to check that in every commit.

[SylvesterWilmott]

Looks good!

Just a couple of things:

1. In the collaborators list, I think we can align the text in the rows to the left side of the screen instead of using the 72dp inset. This gives more space for the email addresses.
2. For markdown enabled notes, the collaborators menu item should be available while in "preview" mode. Currently, it's only shown in the menu while in "Edit" mode.

[danilo04]

Hi @SylvesterWilmott, thanks for the review.

In the collaborators list, I think we can align the text in the rows to the left side of the screen instead of using the 72dp inset. This gives more space for the email addresses.

Fixed in 98189e5.

For markdown enabled notes, the collaborators menu item should be available while in "preview" mode. Currently, it's only shown in the menu while in "Edit" mode.

Fixed in 251e7e1.

[SylvesterWilmott]

Looks good! Thanks @danilo04

[ParaskP7]

👋 @danilo04 !

All LGTM, thanks for applying mine and Sylvester's suggestions, still approved on my part! 🥇