Implement Null Object Pattern for Optional Dependencies

[frogr]

Problem

Lots of nil checking throughout the codebase.

Tasks

• Create null objects for Subscription
• Implement null Plan object
• Add null user for guest behavior
• Replace nil checks with null objects

Acceptance Criteria

• Create app/models/null/ directory
• No more &. operators for subscriptions
• Null objects implement same interface
• All specs pass with null objects
• Add unit tests for null objects

Files to modify

• Various controllers and views checking for nil
• Create null object classes

Phase: 3 (Infrastructure)
Priority: Low