feat(openapi): support structured properties & forms

[david-leifker]

All changes refer to the DataHub OpenAPI v2 endpoints.

Strongly Typed Endpoints:

• Forms entity & aspects

Generic Endpoints:

• Structured Properties support
• Experimental generic PATCH support
• Relationships read support
• Timeseries aspects read support

Docs:

• Structured Properties OpenAPI v2 Guide

Notes:

This typeref union prevents a strong-typed Structured Properties OpenAPI implementation. Possible fix in the future by not having to rely on the avro -> json schema transformation.

Example PATCH:

curl -X 'PATCH' -v \
  'http://localhost:8080/openapi/v2/entity/dataset/urn%3Ali%3Adataset%3A%28urn%3Ali%3AdataPlatform%3Ahive%2CSampleHiveDataset%2CPROD%29/structuredProperties' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json-patch+json' \
  -d '{
        "patch": [
            {
                "op": "remove",
                "path": "/properties/urn:li:structuredProperty:my.test.MyProperty01"
            }
        ],
        "arrayPrimaryKeys": {
            "properties": [
                "propertyUrn"
            ]
        }
      }' | jq

Checklist

• The PR conforms to DataHub's Contributing Guideline (particularly Commit Message Format)
• Links to related issues (if applicable)
• Tests for the changes have been added/updated (if applicable)
• Docs related to the changes have been added/updated (if applicable). If a new feature has been added a Usage Guide has been added for the same.
• For any breaking change/potential downtime/deprecation/big changes an entry has been made in Updating DataHub