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/// @startDocuBlock JSF_api_user_create
/// @brief Create a new user.
///
/// @RESTHEADER{POST /_api/user, Create User}
///
/// @RESTDESCRIPTION
///
/// The following data need to be passed in a JSON representation in the body
/// of the POST request:
///
/// - *user*: The name of the user as a string. This is mandatory.
/// - *passwd*: The user password as a string. If no password is specified, the
///   empty string will be used. If you pass the special value
///   *ARANGODB_DEFAULT_ROOT_PASSWORD*, the password will be set the value
///   stored in the environment variable `ARANGODB_DEFAULT_ROOT_PASSWORD`. This
///   can be used to pass an instance variable into ArangoDB. For example, the
///   instance identifier from Amazon.
/// - *active*: An optional flag that specifies whether the user is active.
///   If not specified, this will default to true
/// - *extra*: An optional JSON object with arbitrary extra data about the user
/// - *changePassword*: An optional flag that specifies whethers the user must
///   change the password or not. If not specified, this will default to false.
///   If set to true, the only operations allowed are PUT /_api/user or PATCH /_api/user.
///   All other operations executed by the user will result in an HTTP 403.
///
/// If the user can be added by the server, the server will respond with HTTP 201.
/// In case of success, the returned JSON object has the following properties:
///
/// - *error*: Boolean flag to indicate that an error occurred (false in this case)
/// - *code*: The HTTP status code
///
/// In case of error, the body of the response will contain a JSON object with additional error details.
/// The object has the following attributes:
///
/// - *error*: Boolean flag to indicate that an error occurred (true in this case)
/// - *code*: The HTTP status code
/// - *errorNum*: The server error number
/// - *errorMessage*: A descriptive error message
///
/// @RESTRETURNCODES
///
/// @RESTRETURNCODE{201}
/// Returned if the user can be added by the server
///
/// @RESTRETURNCODE{400}
/// If the JSON representation is malformed or mandatory data is missing from the request.
///
/// @endDocuBlock
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