[POC] Use DynamoDB as a metadata store for Flow Framework system indices

[dbwiddis]

This PR is for educational/reference purposes only.

Do not merge this PR.

Description

Demonstrates the ability to use DynamoDB in place of OpenSearch system indices for the Flow Framework plugin

• Migrated all APIs except “search”
• Minimal changes to plugin code for create, index, get, and delete APIs using a wrapper client
• Some changes required to WorkflowState class to handle updating state with get/modify/put sequence

Setup

1. Uses a local DynamoDB instance running in a Docker container. Follow setup instructions here: https://github.com/awslabs/amazon-dynamodb-local-samples?tab=readme-ov-file#running-dynamodb-local-as-a-docker-image
2. Update src/main/plugin-metadata/plugin-security.policy as appropriate (this PR got a minimal config needed, it can probably be tuned or better restricted)

Demo

Created (POST) and updated (PUT) a template for a chat agent using ML Commons. Used GET to read the template and (unprovisioned) state. Provisioned the template and queried the resources:

{
    "workflow_id": "Gk9Ako4Bqm_TOBvIrImu",
    "state": "COMPLETED",
    "provisioning_progress": "DONE",
    "provision_start_time": 1711850695907,
    "provision_end_time": 1711850704738,
    "resources_created": [
        {
            "resource_id": "G09Ako4Bqm_TOBvIsYkc",
            "resource_type": "connector_id",
            "workflow_step_id": "create_connector_1",
            "workflow_step_name": "create_connector"
        },
        {
            "resource_id": "Hk9Ako4Bqm_TOBvIw4kO",
            "resource_type": "model_id",
            "workflow_step_name": "register_remote_model",
            "workflow_step_id": "register_model_2"
        },
        {
            "resource_id": "Hk9Ako4Bqm_TOBvIw4kO",
            "resource_type": "model_id",
            "workflow_step_id": "register_model_2",
            "workflow_step_name": "deploy_model"
        },
        {
            "resource_id": "IE9Ako4Bqm_TOBvIzYmZ",
            "resource_type": "agent_id",
            "workflow_step_name": "register_agent",
            "workflow_step_id": "sub_agent"
        },
        {
            "resource_id": "IU9Ako4Bqm_TOBvIz4kU",
            "resource_type": "agent_id",
            "workflow_step_id": "root_agent",
            "workflow_step_name": "register_agent"
        }
    ]
}

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[dbwiddis]

Closing this PR as it's served its purpose and is unlikely to be iterated on.

It will remain here for reference for a potential future datastore-as-index integration!