[FEATURE] Remove user_inputs field from template and set values directly for each workflow

[joshpalis]

The current use case template includes a user_inputs field, whose values can be used throughout the template in cases where this particular value may be used multiple times. For instance, the model_id or index_name can potentially be used in several areas.

This comes with a few issues regarding parsing, and ascertaining the values of a given field such as user_inputs.index_name during the execution of a WorkflowStep.

To reduce complexity, it's necessary to remove the user_inputs section of the use case template and just set those values directly.

For instance, the previous use case template to create an ingest pipeline and index (with created ingest pipeline set as the default ingest pipeline) :

{
  "name": "semantic-search",
  "description": "My semantic search use case",
  "use_case": "SEMANTIC_SEARCH",
  "operations": [
    "PROVISION"
  ],
  "version": {
    "template": "1.0.0",
    "compatibility": [
      "2.9.0",
      "3.0.0"
    ]
  },
  "user_inputs": {
    "index_name": "my-knn-index",
    "pipeline_id": "my-ingest-pipeline"
  },
  "workflows": {
    "provision": {
      "nodes": [
        {
          "id": "workflow_step_1",
          "type": "create_ingest_pipeline",
          "inputs": {
            "id": "user_inputs.pipeline_id",
            "description": "some description",
            "processors": [
              {
                "type": "text_embedding",
                "params": {
                  "model_id": "my-existing-model-id",
                  "input_field_name": "text_passage",
                  "output_field_name": "text_embedding"
                }
              }
            ]
          }
        },
        {
          "id": "workflow_step_2",
          "type": "create_index",
          "inputs": {
            "name": "user_inputs.index_name",
            "settings": "{\"index.knn\":true,\"default_pipeline\":\"user_inputs.pipeline_id\"}"
          }
        }
      ],
      "edges": [
        {
          "source": "create_ingest_pipeline",
          "dest": "create_index"
        }
      ]
    }
  }
}

Proposed use case template (without user inputs) :

{
  "name": "semantic-search",
  "description": "My semantic search use case",
  "use_case": "SEMANTIC_SEARCH",
  "operations": [
    "PROVISION"
  ],
  "version": {
    "template": "1.0.0",
    "compatibility": [
      "2.9.0",
      "3.0.0"
    ]
  },
  "workflows": {
    "provision": {
      "nodes": [
        {
          "id": "workflow_step_1",
          "type": "create_ingest_pipeline",
          "inputs": {
            "id": "my-ingest-pipeline",
            "description": "some description",
            "processors": [
              {
                "type": "text_embedding",
                "params": {
                  "model_id": "my-existing-model-id",
                  "input_field_name": "text_passage",
                  "output_field_name": "text_embedding"
                }
              }
            ]
          }
        },
        {
          "id": "workflow_step_2",
          "type": "create_index",
          "inputs": {
            "name": "my-knn-index",
            "settings": "{\"index.knn\":true,\"default_pipeline\":\"my-ingest-pipeline\"}"
          }
        }
      ],
      "edges": [
        {
          "source": "create_ingest_pipeline",
          "dest": "create_index"
        }
      ]
    }
  }
}