feat: Implement support for creating simple policy fragments

[FilPag]

Policy Fragments Implementation

Updated [Document] attribute to include type parameter for distinguishing between policy documents and policy fragments.

Changes

• type: DocumentType.Fragment - Creates policy file with <fragment> as root tag
• type: DocumentType.Policy - Creates policy file with <policies> as root tag (default if no parameter is defined)

Example Usage

[Document("authentication-fragment", type: DocumentType.Fragment)]
public class AuthenticationFragment : IFragment
{
    public void Fragment(IFragmentContext context)
    {
        context.SetHeader("X-Auth-Fragment", "true");
        context.AuthenticationBasic("{{username}}", "{{password}}");
    }
}

Compilation Output

Fragment (DocumentType.Fragment):

<fragment>
  <set-header name="X-Auth-Fragment" exists-action="override">
    <value>true</value>
  </set-header>
  <authentication-basic username="{{username}}" password="{{password}}" />
</fragment>

Policy (DocumentType.Policy - default):

<policies>
  <inbound>
    <!-- policies here -->
  </inbound>
</policies>

[Mielek]

@FilPag Thank you so much for this contribution. We appreciate your time and effort doing that.

Change looks really nice. It is as well prepared for the emulator which we plan on doing. I think with minor change which I posted in one of the file we can merge it. I think this change would make tests pass.

Would you mind creating some example Fragment in the example project? It is not a blocker but It would allow other folks which want to only use the library easy way of seeing how to create a fragment.

Note for future me. It is not needed here. Adding IncludeFragment override method in interfaces (eg context.InlineFragment() or context.InlineFragment(new SomeFragment())) and handling it in compiler would allow easy way to include fragments in policies without remembering string names of the fragment.

[Mielek]

Thank you so much for your contribution!