Support HTTPS proxies and authentication

[fullben]

Does this plugin support authentication with the remote it is trying to acquire dependencies from?

[nedtwigg]

It does not currently, but that could be added. HTTP clients are created in two places:

1. for downloading p2 metadata
   

   equo-ide/solstice/src/main/java/dev/equo/solstice/p2/P2Client.java

   Lines 57 to 63 in 7606cee

   	if (cachingPolicy.cacheAllowed()) {
   	metadataResponseCache = new Cache(new File(p2metadata, "connection"), maxSize);
   	metadataClient = new OkHttpClient.Builder().cache(metadataResponseCache).build();
   	} else {
   	metadataResponseCache = null;
   	metadataClient = new OkHttpClient.Builder().build();
   	}

2. for downloading the actual jars
   

   equo-ide/solstice/src/main/java/dev/equo/solstice/p2/JarCache.java

   Lines 25 to 26 in 7606cee

   	final OkHttpClient client = new OkHttpClient.Builder().build();
   	final P2ClientCache cachingPolicy;

Happy to merge a PR which adds auth support. Ideally we would copy whatever environment variables Eclipse p2 and Tycho are currently using for this, not sure how they handle it.

[lkoe]

Landed via spotless-gradle-plugin and having an interest in this functionality.

Proxy doesn't seem to be an issue as standard java proxy properties (e.g. http.proxyHost...) are honored but we are required to mirror the eclipse p2 repository from a central artifactory server requiring authentication.
Effectively this currently prevents us from using newer spotless versions :-|