Goals

Add a `proxy:` field to the `http` output where the user can provide a proxy URL to be used by that output only.

Non-Goals

Not using HTTP_PROXY and related environment variables:

• Allow separate outputs to use different proxy settings.
• Keep all configuration in the resource, avoid hidden effects.
• Avoid potential confusion caused by default proxy environment settings inherited from some othersource. 
• Avoid potential future bugs if HTTP_PROXY env. vars are accidentally ignored (easy to do if not using the http.DefaultTransport)

Motivation

Initial use case is HCP logs being forwarded from management to guest clusters. This requires the use of a specific proxy.

This is no an unusual use case, the features is likely to be needed in other settings.

Alternatives

None

Acceptance Criteria

• Forward logs to a HTTP receiver via a HTTP proxy.

Risk and Assumptions

Low risk, straightforward implementation. 

Need to add the API field and copy the URL value to http.Transport.Proxy when setting up the HTTP connection.

Documentation Considerations

One new field.