New dart library for onboarding flow logic

[murali-shris]

Is your feature request related to a problem? Please describe.

We have onboarding logic duplication in at_onboarding_cli (at_onboarding_service_impl.dart
) and at_client_mobile (at_client_service.dart)

Describe the solution you'd like

Create a common package that eliminates code duplication at_onboarding_cli and at_client_mobile

Describe alternatives you've considered

No response

Additional context

No response

[murali-shris]

Code duplication between at_onboarding_cli, at_onboarding_flutter, at_client_service

At_onboarding_flutter → onboarding_service.dart
Onboard method
Calls at_client_service.onboard(..)
Authenticate method
Check atsign server status
Calls at_client_service.authenticate

At_onboarding_cli → at_onboarding_service_impl.dart
Onboard method

• Checks for secondary address in root server
• Cram authentication using at_lookup
• If cram auth is successful
• Generate encryption key pair and self encryption key
• If auth mode is sim, read public key from at_chops
• Create .atKeys file from key pairs
• Update pkam public key to remote secondary
• Create atchops(if not injected) and init at_client
• Try pkam auth to server
• If pkam auth is success, update encryption public key to server. Delete cram from server

authenticate method

• Read atKeysfile
• init at_chops(if not injected) and at_client
• Pkam auth to server
• Persist keys to local secondary

At_client_mobile → at_client_service.dart (trunk code - no support for pkam secure element)

onboard method //wrong method naming. This method does auth from biometric/atkeys file

• Create at_chops from atKeys file
• Create at_client
• Read keys from biometric and store to local secondary
• getKeyRestorePolicy. If activate or restore throw exception

Authenticate method

• If cram secret is not set in preference, read keys from .atKeys file, perform pkam auth, store keys to biometric storage
• If cram secret is set,
• Perform cram auth
• Generate pkam key pair
• Update pkam public key to server
• Perform pkam auth
• If pkam is success, store keys to biometric, generate encryption keypair, generate self encryption key, delete cram secret from server
• Create at_chops and at client
• Persist keys to local secondary

Feature specific to flutter in at_client mobile

• Persisting to biometric storage
• Reading from biometric storage

Features common to at_client_service and at_onboarding_cli

• Cram auth
• Keypair generation
• Pkam auth
• Persisting to local secondary
• Generating .atKeysFile
• Reading from .atKeysFile