Improvements to sync behavior documentation

[andrew-kolesnikov]

Overview of issue:
In some scenarios, resources modified at destination are ignored during the sync which results in drift between source and destination configurations.

Proposed changes:

• Documentation to address this behavior explicitly
• Provide recommendations for scenarios where drift occurs

[heyronhay]

Hey Andrew! Thanks for the info - mind clarifying a bit?

Are you expecting modifications of destination resources to be synced back to the source? sync-cli is meant to be a source->destination sync, and modifications to destination resources shouldn't be synced back to the source.

Or maybe you are meaning something else?

[andrew-kolesnikov]

@heyronhay I understand that only uni-directional sync is supported. When resources are modified at both source and destination, the source->destination sync appears to then silently ignore them, which creates unwanted (and invisible) drift between the source and destination