Add `BadgerDBCreatePipeline` method for `PipelineModel`

[jim-junior]

Description

Extend the PipelineModel struct by implementing a new standalone method called BadgerDBCreatePipeline. To prevent breaking changes across the codebase, do not refactor or replace the existing etcd-based CreatePipeline implementation. This method introduces native support for serializing and persisting a new pipeline payload directly inside BadgerDB.

Requirements

• File Location: internal/models/pipeline.go
• Method Signature Strategy: Introduce a new method named BadgerDBCreatePipeline(pipeline *types.Pipeline) error on the PipelineModel struct.
• Transactionality: Execute both the duplication check and the write sequence within a single BadgerDB Update (write) transaction to guarantee execution safety.
• Uniqueness Constraint: * Before saving the bytes, inspect the database to check if the calculated lookup key already exists.
  • If the key exists, return a descriptive custom error indicating that a pipeline with that name is already defined, preventing accidental overwrites.
• Serialization & Key Generation: * Generate the targeted storage key using the format: /pipelines/{pipeline.Name}.
  • Marshal the incoming *types.Pipeline struct into JSON bytes using the standard json.Marshal library.
• Testing: Add a dedicated unit test suite inside internal/models/pipeline_test.go to validate successful creation workflows, persistence checks, and key-conflict validation pathways using an in-memory database instance.

Success Criteria

• The BadgerDBCreatePipeline method is added cleanly alongside legacy methods without breaking public structure boundaries.
• The existence lookups and persistence writes occur atomically within an exclusive write transaction block.
• Attempting to write a pipeline name that is already allocated correctly triggers a duplicate error barrier.
• Test Case implementation: A comprehensive unit test is provided that:
  • Sets up an isolated, in-memory BadgerDB instance.
  • Successfully calls BadgerDBCreatePipeline with a valid mock pipeline object.
  • Confirms that the output is accurately stored as unmarshaled JSON data matching the input properties.
  • Asserts that submitting an identical pipeline struct second-in-line accurately rejects the write with a key collision error response.