Support model references directly to primitives

A model like this:

swagger: '2.0'
definitions:
  User:
    $ref: 'BaseUser'
  BaseUser:
    type: string

Is legal but currently not supported in the parser.

[jbx1]

While direct references to primitives are supported, none of the validation specifiers associated with it are carried over.

For example:

     email:
        type: string
        pattern: '^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\.[a-zA-Z0-9-]+)*$'
        description: Email address of the customer.
     mobile:
        $ref: '#/definitions/Mobile'

with the definition:

 Mobile:
    type: string
    pattern: '^\\+[1-9][0-9]{3,14}$'
    description: The mobile number in E.164 format.

Using swagger-codegen version 2.3.1 for spring-boot generates the right validation annotations and javadoc for email:

  /**
   * Email address of the customer.
   * @return email
  **/
  @ApiModelProperty(value = "Email address of the customer.")
@Pattern(regexp="^[a-zA-Z0-9.!#$%&’*+/=?^_`{|}~-]+@[a-zA-Z0-9-]+(?:\\.[a-zA-Z0-9-]+)*$") 
  public String getEmail() {
    return email;
  }

But not for the mobile property:

/**
   * Get mobile
   * @return mobile
  **/
  @ApiModelProperty(required = true, value = "")
  @NotNull
  public String getMobile() {
    return mobile;
  }

[jimvmathews]

@fehguy - Can you point us to the PR or test that has fixed this issue? I have pulled this latest version into the swagger-codegen and the problem https://github.com/swagger-api/swagger-codegen/issues/3483 is not resolved.