GET /v3/api-docs (ungrouped, default), operation at /accounts/{id}:
  operationId        = getAccountV2  (picked from ONE of the three handlers, not versioned itself)
  response schema    = oneOf [3 entries]: #/components/schemas/AccountV1, #/components/schemas/AccountV2, #/components/schemas/AccountV1Point1
  API-Version header enum (auto-documented) = ["2","1","1.0.0","1.1"]
  API-Version header default                = "1.0.0"

Full raw document:
{
  "openapi" : "3.1.0",
  "info" : {
    "title" : "OpenAPI definition",
    "version" : "v0"
  },
  "servers" : [ {
    "url" : "http://localhost:36991",
    "description" : "Generated server url"
  } ],
  "paths" : {
    "/accounts/{id}" : {
      "get" : {
        "tags" : [ "account-controller" ],
        "operationId" : "getAccountV2",
        "parameters" : [ {
          "name" : "id",
          "in" : "path",
          "required" : true,
          "schema" : {
            "type" : "string"
          }
        }, {
          "name" : "API-Version",
          "in" : "header",
          "schema" : {
            "type" : "string",
            "default" : "1.0.0",
            "enum" : [ "2", "1", "1.0.0", "1.1" ]
          }
        } ],
        "responses" : {
          "200" : {
            "description" : "OK",
            "content" : {
              "*/*" : {
                "schema" : {
                  "oneOf" : [ {
                    "$ref" : "#/components/schemas/AccountV1"
                  }, {
                    "$ref" : "#/components/schemas/AccountV2"
                  }, {
                    "$ref" : "#/components/schemas/AccountV1Point1"
                  } ]
                }
              }
            }
          }
        }
      }
    },
    "/widgets/{id}" : {
      "get" : {
        "tags" : [ "widget-handler" ],
        "operationId" : "getWidgetV1",
        "responses" : {
          "200" : {
            "description" : "OK",
            "content" : {
              "*/*" : {
                "schema" : {
                  "$ref" : "#/components/schemas/ServerResponse"
                }
              }
            }
          }
        }
      }
    }
  },
  "components" : {
    "schemas" : {
      "AccountV2" : {
        "type" : "object",
        "description" : "Account shape served by API version 2 — restructured, nested contact object",
        "properties" : {
          "accountId" : {
            "type" : "string",
            "description" : "Account identifier"
          },
          "displayName" : {
            "type" : "string",
            "description" : "Account holder display name"
          },
          "contact" : {
            "$ref" : "#/components/schemas/Contact",
            "description" : "Nested contact details, replacing the flat email field from 1.1"
          },
          "status" : {
            "type" : "string",
            "description" : "Lifecycle status, new in v2",
            "enum" : [ "ACTIVE", "SUSPENDED", "CLOSED" ]
          },
          "apiVersion" : {
            "type" : "string",
            "description" : "Echoes the resolved API version"
          }
        }
      },
      "Contact" : {
        "type" : "object",
        "description" : "Contact details nested under an account, v2+",
        "properties" : {
          "email" : {
            "type" : "string",
            "description" : "Contact email"
          }
        }
      },
      "AccountV1" : {
        "type" : "object",
        "description" : "Account shape served by API version 1",
        "properties" : {
          "id" : {
            "type" : "string",
            "description" : "Account identifier"
          },
          "name" : {
            "type" : "string",
            "description" : "Account holder name"
          },
          "apiVersion" : {
            "type" : "string",
            "description" : "Echoes the resolved API version"
          }
        }
      },
      "AccountV1Point1" : {
        "type" : "object",
        "description" : "Account shape served from API version 1.1 onward (baseline handler)",
        "properties" : {
          "id" : {
            "type" : "string",
            "description" : "Account identifier"
          },
          "name" : {
            "type" : "string",
            "description" : "Account holder name"
          },
          "email" : {
            "type" : "string",
            "description" : "Contact email, added in 1.1"
          },
          "apiVersion" : {
            "type" : "string",
            "description" : "Echoes the resolved API version"
          }
        }
      },
      "ServerResponse" : { }
    }
  }
}