Reworked Send screen logic

[myxmaster]

Description

Fixed several problems and improved back press handling of Send screen.

First problem (#1974): When balance is 0, the send button is enabled although sending cannot succeed.
Second problem: When a destination is entered and proceed is clicked, you can change the destination afterwards to another type (BTC <-> LN), but the dialog does not adjust to the new destination type.

Fixed the first problem by disabling the send button if balance is zero.

Fixed the second problem by making the destination read-only after proceed is clicked. To change the destination, the user now can go back which now clears the input and allows entering a new destination. However, if the Send screen was entered by scanning a QR code or from the Contacts screen, the back button still closes the Send screen.

Before:

Same address, different (wrong) destination type:

After:

This pull request is categorized as a:

• New feature
• Bug fix
• Code refactor
• Configuration change
• Locales update
• Quality assurance
• Other

Checklist

• I’ve run yarn run tsc and made sure my code compiles correctly
• I’ve run yarn run lint and made sure my code didn’t contain any problematic patterns
• I’ve run yarn run prettier and made sure my code is formatted correctly
• I’ve run yarn run test and made sure all of the tests pass

Testing

If you modified or added a utility file, did you add new unit tests?

• No, I’m a fool
• Yes
• N/A

I have tested this PR on the following platforms (please specify OS version and phone model/VM):

• Android
• iOS

I have tested this PR with the following types of nodes (please specify node version and API version where appropriate):

• Embedded LND
• LND (REST)
• LND (Lightning Node Connect)
• Core Lightning (c-lightning-REST)
• LndHub
• [DEPRECATED] Core Lightning (Spark)
• [DEPRECATED] Eclair

Locales

• I’ve added new locale text that requires translations
• I’m aware that new translations should be made on the ZEUS Transfix page and not directly to this repo

Third Party Dependencies and Packages

• Contributors will need to run yarn after this PR is merged in
• 3rd party dependencies have been modified:
  • verify that package.json and yarn.lock have been properly updated
  • verify that dependencies are installed for both iOS and Android platforms

Other:

• Changes were made that require an update to the README
• Changes were made that require an update to onboarding

[kaloudis]

I like the idea but we have to think about what payment flows are going to look like as we target external accounts + signers in v0.9.0

[myxmaster]

Ok, but do you have any specific concerns in regards to this PR? Right now it is definitely buggy and it shouldn't stay like this.

[kaloudis]

This looks great, but let's remove the colon (:) from the Fee label instead of adding it to the other fields.

Let's stay consistent with the rest of the app.

[kaloudis]

Let's also grey out, or completely remove the paper airplane icon on the send button when it is disabled

[myxmaster]

Done. Also fixed a layout bug which led to a cut-off send button.