feat(policy object selectors): adds initial selector protos, moves policy object type messages to top-level to avoid circular imports, and provides subject mappings in response to GetAttributeValuesByFqns

[jakedoublev]

Partially addresses #366

Supplies subject mappings / condition sets back for specified value provided in GetAttributeValuesByFqns

Request:

grpcurl -plaintext -d '{"fqns":["https://example.com/attr/attr1/value/value2"],"with_value":{"with_subject_maps":true}}' localhost:9000 policy.attributes.AttributesService.GetAttributeValuesByFqns

Response:

{
  "fqnAttributeValues": {
    "https://example.com/attr/attr1/value/value2": {
      "attribute": {
        "id": "6a261d68-0899-4e17-bb2f-124abba7c09c",
        "namespace": {
          "id": "8f1d8839-2851-4bf4-8bf4-5243dbfe517d",
          "name": "example.com"
        },
        "name": "attr1",
        "rule": "ATTRIBUTE_RULE_TYPE_ENUM_ANY_OF",
        "values": [
          {
            "id": "74babca6-016f-4f3e-a99b-4e46ea8d0fd8",
            "value": "value1",
            "active": true
          },
          {
            "id": "2fe8dea1-3555-498c-afe9-99724f35f3d3",
            "value": "value2",
            "members": [
              "0fd363db-27b1-4210-b77b-8c82fe044d41",
              "532e5957-28f7-466d-91e2-493e9431cd83"
            ],
            "fqn": "https://example.com/attr/attr1/value/value2",
            "active": true
          }
        ],
        "active": true,
        "metadata": {
          
        }
      },
      "value": {
        "id": "2fe8dea1-3555-498c-afe9-99724f35f3d3",
        "value": "value2",
        "members": [
          "0fd363db-27b1-4210-b77b-8c82fe044d41",
          "532e5957-28f7-466d-91e2-493e9431cd83"
        ],
        "fqn": "https://example.com/attr/attr1/value/value2",
        "active": true,
        "subjectMappings": [
          {
            "id": "e6a3f940-e24f-4383-8763-718a1a304948",
            "subjectConditionSet": {
              "id": "798aacd2-abaf-4623-975e-3bb8ca43e318",
              "subjectSets": [
                {
                  "conditionGroups": [
                    {
                      "conditions": [
                        {
                          "subjectExternalField": "department",
                          "operator": "SUBJECT_MAPPING_OPERATOR_ENUM_IN",
                          "subjectExternalValues": [
                            "marketing",
                            "sales"
                          ]
                        },
                        {
                          "subjectExternalField": "role",
                          "operator": "SUBJECT_MAPPING_OPERATOR_ENUM_IN",
                          "subjectExternalValues": [
                            "senior_vice_president",
                            "vice_president",
                            "director"
                          ]
                        }
                      ],
                      "booleanOperator": "CONDITION_BOOLEAN_TYPE_ENUM_AND"
                    }
                  ]
                }
              ]
            },
            "actions": [
              {
                "standard": "STANDARD_ACTION_TRANSMIT"
              },
              {
                "standard": "STANDARD_ACTION_DECRYPT"
              }
            ]
          }
        ]
      }
    }
  }
}

[jakedoublev]

Closes #276