New Caller Type, Helpers

[matoszz]

• Introduces a unified caller identity type that represents any request actor through a single, consistent interface rather than a fragmented set of context types
• Replaces boolean privilege flags with named, explicitly valued constants that remain stable as new permissions are added over time
• System administrator status is now a first-class permission rather than a loosely coupled boolean, making privilege checks consistent with how all other bypass logic is handled
• Provides a migration bridge that converts the existing authenticated user context into the new type, allowing core to adopt the new model incrementally
• Establishes the foundation for collapsing the large surface of field-specific context accessor functions in core down to a single context lookup with direct field access

Related to theopenlane/utils#125

[sonarqubecloud]

Quality Gate failed

Failed conditions
5.8% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud