View messages on Field app

[vinayvenu]

Story

As a field user, I would like to see Whatsapp messages sent to a user's phone so that I can send a new message when required

See epic for details on UI

Acceptance criteria

• When Glific messaging is enabled for an organisation, the Whatsapp button is shown on the Subject Dashboard
• The Whatsapp button is shown only when the subject has a number stored
• When touched, the Whatsapp button takes you to the "Messages" Screen
• The Messages screen has two tabs : messages scheduled and messages sent
• Back Navigation works fine from all screens
• Section-wise list for sentMessages
• Flat list of scheduledMessages
• All texts have translations in major languages
• When nothing available, the app shows a message "No Messages Scheduled" or "No Messages Sent".
• If app cannot connect to the server, a message "Could not retrieve messages" is shown
• While the app is retrieving messages, a spinner is shown on the screen
• App does not retrieve messages when on the Subject Dashboard screen

Tech tasks

• Reuse existing API for web (create different endpoint)
• UI/UX for showing screens
• Spinner
• No data available
• Internet not available
• Translations
• Navigation
• Tabs (dont reload on tab switch)