Add `BadgerDBFindAll` method for `ResourceDefinitionModel`

[jim-junior]

Description

Extend the ResourceDefinitionModel struct by implementing a new standalone method called BadgerDBFindAll. To maintain strict backward compatibility across the rest of the engine, do not modify or deprecate the existing etcd-based FindAll implementation. This new method will introduce standalone support to iterate through and retrieve all resource definitions stored under the specified namespace prefix directly from BadgerDB.

Requirements

• File Location: internal/models/resource_definitions.go
• Method Signature Strategy: Introduce a new method named BadgerDBFindAll() ([]string, error) on the ResourceDefinitionModel struct.
• Transactionality: Execute the prefix scan entirely within a BadgerDB View (read-only) transaction.
• Prefix Scanning:
  • Instantiate a database iterator using default options via txn.NewIterator(badger.DefaultIteratorOptions).
  • Prefix scan using the standard byte boundary matching the legacy prefix namespace: /resource_definitions/.
• Data Processing & Lifecycle Rules:
  • Loop through matched database items, retrieving the raw payloads safely.
  • Ensure you adhere to BadgerDB's item evaluation lifecycle rules by copying data safely out of the transaction scope (e.g., using item.ValueCopy()).
  • Append the string representation of each definition payload to a collection slice.
• Error Handling: If no keys match the designated prefix context, return a descriptive custom error: fmt.Errorf("no resource definitions found") to guarantee parity with the etcd counterpart.
• Testing: Write a dedicated unit test suite inside internal/models/resource_definitions_test.go to validate standalone dataset discovery.

Success Criteria

• The BadgerDBFindAll method is successfully added to the data layer model alongside legacy paths without modifying existing API signatures.
• The engine correctly sweeps keys using a BadgerDB transaction iterator targeted exclusively at the /resource_definitions/ byte prefix.
• Searching a database containing zero records under the target prefix properly drops out with the custom "no resource definitions found" error validation.
• Test Case implementation: A comprehensive unit test is provided that:
  • Seeds an isolated, in-memory BadgerDB instance with multiple disparate resource configuration payloads.
  • Successfully queries BadgerDBFindAll and verifies the array length matches the seeded database state perfectly.
  • Asserts that all returned payload strings match the values initially injected.
  • Confirms that calling the method against a completely clean database structure securely passes back the required error message.