Add flattenNamespaces transformer

[srchase]

Adds flattenNamespaces transformer that flattens the namespaces of shapes connected to a specified service in a model into a target namespace. Shapes that are not connected to the service will not be flattened, unless they have been tagged with a tag that has been included in the includeTagged configuration list. Tagged shapes that conflict with an existing shape within the service closure will not be flattened.

Example configuration:

{
    "version": "1.0",
    "projections": {
        "exampleProjection": {
            "transforms": [
                {
                    "name": "flattenNamespaces",
                    "args": {
                        "namespace": "ns.foo",
                        "service": "ns.foo#MyService,
                        "includeTagged": ["include", "conflict"],
                    }
                }
            ]
        }
    }
}

Input model:

{
  "smithy": "1.0",
  "shapes": {
    "ns.foo#MyService": {
      "type": "service",
      "version": "2017-01-19",
      "operations": [
        {
          "target": "ns.bar#MyOperation"
        }
      ]
    },
    "ns.bar#MyOperation": {
      "type": "operation",
      "output": {
        "target": "ns.baz#MyOperationOutput"
      }
    },
    "ns.baz#MyOperationOutput": {
      "type": "structure",
      "members": {
        "foo": {
          "target": "smithy.api#String"
        }
      }
    },
    "ns.corge#UnconnectedFromService": {
      "type": "string",
      "traits": {
        "smithy.api#tags": ["include"]
      }
    },
    "ns.corge#MyOperationOutput": {
      "type": "string",
      "traits": {
        "smithy.api#tags": ["conflict"]
      }
    },
    "ns.corge#AnotherString": {
      "type": "string",
      "traits": {
        "smithy.api#tags": ["ignored"]
      }
    }
  }
}

Transformed model:

{
  "smithy": "1.0",
  "shapes": {
    "ns.foo#MyService": {
      "type": "service",
      "version": "2017-01-19",
      "operations": [
        {
          "target": "ns.foo#MyOperation"
        }
      ]
    },
    "ns.foo#MyOperation": {
      "type": "operation",
      "output": {
        "target": "ns.foo#MyOperationOutput"
      }
    },
    "ns.foo#MyOperationOutput": {
      "type": "structure",
      "members": {
        "foo": {
          "target": "smithy.api#String"
        }
      }
    },
    "ns.foo#UnconnectedFromService": {
      "traits": {
        "smithy.api#tags": ["include"]
      }
    }
  }
}

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.