Adds default property values in ASP .NET Core models

Created by: james-beer

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
• Filed the PR against the correct branch: master, 4.1.x, 5.0.x. Default: master.
• Copied the technical committee to review the pull request if your PR is targeting a particular programming language.

Description of the PR

Changes

• Addresses #3359 (closed)
• Also fixes a small syntax error in docker-entrypoint.sh.

Tests

• ./run-in-docker.sh mvn package successfully builds & runs tests.
• ./run-in-docker.sh generate ... produces the following.

Schema

openapi: '3.0.0'
info:
  version: 1.0.0
  title: API with Default Values
servers:
  - url: http://localhost:8080
paths:
  /test:
    post:
      operationId: testDefaults
      requestBody:
        required: true
        content:
          application/json:
            schema:
              '$ref': '#/components/schemas/Payload'
      responses:
        '200':
          description: Ok
components:
  schemas:
    Payload:
      type: object
      properties:
        stringProp:
          type: string
          default: foo
        intProp:
          type: integer
          default: 123
        floatProp:
          type: number
          format: float
          default: 1.23
        doubleProp:
          type: number
          format: double
          default: 1.234
        decimalProp:
          type: number
          format: decimal
          default: 1.2345
        enumProp:
          type: string
          enum: [One, Two, Three]
          default: Two

Generated model properties

[DataContract]
public partial class Payload : IEquatable<Payload>
{ 
    /// <summary>
    /// Gets or Sets StringProp
    /// </summary>
    [DataMember(Name="stringProp", EmitDefaultValue=false)]
    public string StringProp { get; set; } = "foo";

    /// <summary>
    /// Gets or Sets IntProp
    /// </summary>
    [DataMember(Name="intProp", EmitDefaultValue=false)]
    public int? IntProp { get; set; } = 123;

    /// <summary>
    /// Gets or Sets FloatProp
    /// </summary>
    [DataMember(Name="floatProp", EmitDefaultValue=false)]
    public float? FloatProp { get; set; } = 1.23F;

    /// <summary>
    /// Gets or Sets DoubleProp
    /// </summary>
    [DataMember(Name="doubleProp", EmitDefaultValue=false)]
    public double? DoubleProp { get; set; } = 1.234D;

    /// <summary>
    /// Gets or Sets DecimalProp
    /// </summary>
    [DataMember(Name="decimalProp", EmitDefaultValue=false)]
    public decimal? DecimalProp { get; set; } = 1.2345M;

    /// <summary>
    /// Gets or Sets EnumProp
    /// </summary>
    [DataMember(Name="enumProp", EmitDefaultValue=false)]
    public EnumPropEnum? EnumProp { get; set; } = EnumPropEnum.TwoEnum;
}

Reviewers

@mandrean, @jimschubert