Improve DnsDialogViewModel nav arguments

[kl]

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This change is 

[linear]

DROID-579 Improve DnsDialogViewModel arguments

[Pururun]

Reviewed 4 of 4 files at r1, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved

[Rawa]

Reviewed 4 of 4 files at r1.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @kl)

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android/app/src/main/kotlin/net/mullvad/mullvadvpn/viewmodel/DnsDialogViewModel.kt line 81 at r1 (raw file):

                viewModelScope,
                SharingStarted.Lazily,
                createViewState(emptyList(), null, false, EMPTY_STRING),

I'm a bit torn of this, I think it would be nicer if we directly show the correct state.

Right now if you click on an existing entry we would incorrectly show EMPTY_STRING first. Maybe it is necessary to introduce a loading state?

Some other remarks that I think we can do better:

• We should review if we can make MutableStateFlow<Settings?> more clear. It doesn't seem to add much in it current form ( except as acting like a cache for the first Settings object we saw to avoid an update as we press save.)
• _ipAddressInput being nullable feels wrong, it looks like the user can input a "null" but that wouldn't be valid input from a user. (It is a backing field and onDnsInputChange only accepts String, but it gets a bit confusing. Maybe lateinit until we get first Settings?
• The following line does a lot of heavy lifting and isn't very readable:

                val input =
                    inputAddress
                        ?: navArgs.index?.let { index -> dnsList[index].addressString() }
                        ?: EMPTY_STRING

E.g that if navArgs.index would either be always null or always a value.

[Rawa]

Reviewed all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @kl)