Credentials should be stored in `EncryptedSharedPreferences`

[bitfireat]

Credentials should be stored in `EncryptedSharedPreferences`

[ArnyminerZ]

The migration and tests for this have been added to #92 😄

[ArnyminerZ]

Note the warning on the docs:

The preference file should not be backed up with Auto Backup. When restoring the file it is likely the key used to encrypt it will no longer be present. You should exclude all EncryptedSharedPreferences from backup using backup rules.

This means that we should provide an option to authorize back again after a device factory reset, or backup restore. Should be taken into account with #4.

Also security-crypto shall be added as dependency:

implementation "androidx.security:security-crypto:1.0.0"

[rfc2822]

When we have the database, I'd just store everything (including credentials) in the private DB. EncryptedSharedPreferences says that it doesn't work across system backup/restore on different devices, but this is a use case that is planned (#4).

Unfortunately we have to store the credentials in clear text for Basic authentication.

[ArnyminerZ]

Then we should store the accounts in Room instead of shared preferences for #76. This means creating a new table, and getting rid of CalendarCredentials.

[rfc2822]

Then we should store the accounts in Room instead of shared preferences for #76. This means creating a new table, and getting rid of CalendarCredentials.

Sounds reasonable :)