Feature/turn off internal fingerprinting

[ORESoftware]

Description of the change

The problem is that "SetFingerprint(v bool)" makes it seem like you are setting the fingerprint value for all items or something, which doesnt make sense.

We should make it more obvious for users to turn on / turn off internal fingerprinting. In my case, I prefer the SDK with my own fingerprint value that I generate manually, so I don't want the Go lib to do the unnecessary work of getting line numbers / filenames from the runtime - I want to turn off all internal fingerprinting, since I use these:

      rollbar.Log(level, s, map[string]interface{}{
		"fingerprint": id,
	})

and then my fingerprint rules are like so:

[
  {
    "condition": {
      "contains": "fingerprint", 
      "path": "custom"
    }, 
    "fingerprint": "{{custom.fingerprint}}", 
    "title": "{{default_title}}"
  }
]

Gianina from Rollbar support says:

Hi Alex! I took a look at the documentation for the Go SDK and the only function available for configuring a custom client side fingerprint is rollbar.SetFingerprint() (https://godoc.org/github.com/rollbar/rollbar-go#Client.SetFingerprint). By default, this function is set to false, so there should not be any fingerprint values sent from your client aside from the one that you are specifying in your rollbar.Log function.

So I guess the fingerprint is created on rollbar servers, not the client, which is pretty intense - I would think that rollbar would do that in the client runtime, and not overburden their servers!

• Bug fix (non-breaking change that fixes an issue)
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[pawelsz-rb]

I think we are introducing more methods. Can we use our existing fingerprinting method and add another optional parameter to indicate we want it from the client?