HTTP Basic authentication on the HTTP source plugin via plugins

[dlvenable]

Description

This PR includes the following significant changes:

• The HTTP Source plugin now supports HTTP Basic authentication.
• Plugins can receive a PluginFactory in their constructor
• A new armeria-common project with pluggable interfaces for extending Armeria servers.
• An Armeria HTTP Basic plugin

The HTTP Source can be configured in the following ways:

1. Without authentication implicitly as it works now:

  source:
    http:

2. Without authentication explicitly:

  source:
    http:
      authentication:
        unauthenticated:

3. With HTTP Basic authentication enabled

  source:
    http:
      authentication:
        http_basic:
          username: log-ingest
          password: s3cr3t

Issues Resolved

Resolves #464

Check List

• New functionality includes testing.
  • All tests pass
• New functionality has been documented.
  • New functionality has javadoc added
• Commits are signed per the DCO using --signoff

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[graytaylor0]

I didn't see any problems. Seems simple and easy to reuse and extend. Nice work!

[chenqi0805]

Just some high level thoughts. The change looks good me.

At this point, having ArmeriaAuthenticationProvider and HttpBasicArmeriaAuthenticationProvider in separate armeria-common module is a bit over-refactoring. For authentication provider interface, I did a brief search on armeria for authentication counterpart in grpc but there seemed to be no findings. So I am not sure whether and how it will be further extended. For HttpBasicArmeriaAuthenticationProvider, I have not seen value outside http-source yet. Thoughts?

[dlvenable]

@chenqi0805 , You are correct that authentication for gRPC is different from HTTP. Though, I believe it also can use HTTP Basic since it uses HTTP underneath.

My primary motivation for refactoring it out is to expose the ArmeriaAuthenticationProvider interface. Users could then write their own authentication mechanism by creating a plugin implementing this interface. But, this is still possible by asking plugin authors to include the http-source plugin in their dependencies. I could move these classes into the http-source plugin now and we can extract them later if needed.

[chenqi0805]

I could move these classes into the http-source plugin now and we can extract them later if needed.

Oh. Not necessary. Just want to hear your thought on this.