Switching to native HttpClient in channel finder client

[georgweiss]

Same comments as #3219

Removed unused methods in ChannelFinderClient

[kasemir]

Removed unused methods in ChannelFinderClient

@shroffk @georgweiss

We're not using the channel finder here, but I have some local tool to import info from our RDB just in case we want to eventually transition to the CF.

Took me a little while to notice that this import tool no longer compiles because this PR changed the API: findByName -> find, set -> update. There is no deleteChannel() method any longer and I cannot figure out how to add a channel. Updating properties and tags of an existing channel is fine, but how do you add or delete a channel?
In the previous API it was further necessary to first create a property, and then it could be assigned to a channel:

cf.set(Property.Builder.property("iocName").owner("fred"));
cf.set(Channel.Builder.channel(channel).with(Property.Builder.property("iocName", "TheIOC));

How is that handled now?
Am I not understanding the API, or are those operations no longer possible, it's mostly read-only, because all the rest is done by python tools or recceiver?

[georgweiss]

I removed methods not referenced n the Phoebus code base. Did not realize other tools may use the API. What method signatures are missing?
Will reinstate them.

[kasemir]

What's missing is a way to add or delete channels.
Channels used to be created like this:

cf.set(Channel.Builder.channel(channel)
                                  .with(Property.Builder.property("iocName", ioc))
                                  .with(Property.Builder.property("time", boot_stamp))
                                  .owner(owner))

and deleted via

cf.deleteChannel(name);

When creating a channel with some property, that property had to already exist, so that "iocName" property used above had to have been created via

cf.set(Property.Builder.property("iocName").owner(owner));

I'm fine with the API changing (findByName -> find, set -> update, ...) but don't currently see a way to add/delete channels, and am unclear if properties and tags already need to exist (if so, how to create them??).

Mind you, there's no desperate rush from my side because we're not really using the CF..
On the other hand, might make sense to have an API that can create stuff. Channel table might not support adding channels now, but why shouldn't it in the future.

[georgweiss]

Ok, maybe just easier to add all of the removed methods.