Allow http/https scheme in otlpexporter endpoint configuration

[alanwest]

Description: otlpexporter endpoint configuration allows for an http or https scheme. The scheme is stripped off when instantiating the gRPC channel. A scheme of https indicates a secure channel. This aligns the collector with this hopefully soon-to-be-merged specification PR open-telemetry/opentelemetry-specification#1729

Link to tracking Issue: #2539

Documentation: Updated readme

[tigrannajaryan]

@alanwest thanks for working on this. Let's merge after open-telemetry/opentelemetry-specification#1729 is merged.

[tigrannajaryan]

Can you please clarify this sentence? I am not sure I understand it.

[alanwest]

Oops, yes I've left out some words, so this sentence makes no sense! Fixed.

The idea is that if you use the scheme https then the insecure setting is ignored. This is inline with the outstanding spec PR open-telemetry/opentelemetry-specification#1729

[alanwest]

@tigrannajaryan I've added a test validating the exporter when the endpoint has an http scheme. I'd like to add a test using the https scheme as well. This would require the test suite to be able to set up its mock receiver configured with TLS.

I noted that the testdata directory contains a certificate but not the corresponding key. Would it be ok to add a cert/key pair in the testdata directory?

The code that sets up the mock receiver is here

opentelemetry-collector/exporter/otlpexporter/otlp_test.go

Lines 75 to 79 in d1fced9

	rcv := &mockTracesReceiver{
	mockReceiver: mockReceiver{
	srv: grpc.NewServer(),
	},
	}

I essentially need to do something like the following to run the test using TLS:

sopts := []grpc.ServerOption{}
creds, _ := credentials.NewServerTLSFromFile(grpctestdata.Path("testdata/test_cert.pem"), grpctestdata.Path("testdata/test_cert_key.pem"))
sopts = append(sopts, grpc.Creds(creds))

rcv := &mockTracesReceiver{
	mockReceiver: mockReceiver{
		srv: grpc.NewServer(sopts...),
	},
}

[tigrannajaryan]

I noted that the testdata directory contains a certificate but not the corresponding key. Would it be ok to add a cert/key pair in the testdata directory?

Yes, I think it is ok.

[bogdandrutu]

Please rebase

[alanwest]

Fixed merge conflicts and added a test using the scheme https. I had to create a new certificate in order to generate the private key. I replaced the existing cert in the testdata directory since it did not seem that it was used anywhere. Is this all good?

[tigrannajaryan]

LGTM. Thank you @alanwest