Adds code coverage reporting for docker-compose based integ tests

Desired Outcome

Current Cobertura coverage results only report coverage for Go unit tests. Our automated tests include integration tests, but the coverage for these integration tests are not being included in coverage reports.

The integration tests use Docker Compose, and have the general form:

                                Conjur
                                    ^
                                    |
                                    V
Test Client Container   <==>  Secretless Broker  <==>   Backend Database
    (client binaries)

We should have either:

Separate coverage for all SB integration tests
Combined coverage results for UT plus integration tests

Or both.

Implemented Changes

Created a Dockerfile for a new, special Secretless Broker image that is compiled with Go coverage instrumentation.
Create a Go test file that wraps the Secretless Broker functionality into a Go test run.
Modified integration tests to create individual test-coverage/cover.out coverage output files for each test.
Created scripts to merge the individual integration test results into one integ test result, and combine integ and UT test results
Refactored the Secretless Broker entrypoint Go code to eliminate CodeClimate complexity errors.
Added calls to these scripts in Jenkins, including archive of HTML output.

The comment that is added to the Secretless Broker Go coverage test file might explain how things are implemented:

// TestCoverage runs the Secretless Broker executable wrapped in a
// Go test so that the Go test infrastructure can collect code coverage stats
// for the Secretless Broker e.g. while running Docker-Compose-based
// integration tests. This Go test and the Secretless Broker code can be
// compiled into a special Secretless Broker test binary that includes
// code coverage instrumentation using the following Go test compile command:
//
//        go test -c -coverpkg="./..." ./cmd/secretless-broker
//
// rather than the usual `go build ...` compile command. (See
// 'Dockerfile.coverage' in the root of this GitHub repository to see how this
// compilation is done and built into a Docker image).
//
// Using this specially-instrumented Secretless Broker test binary, the
// Go test with its embedded Secretless Broker functionality would be invoked
// e.g. using the following command (note that standard Go test parameters
// must be prefixed with '-test.' for images compiled via 'go test -c ...'):
//
//        /usr/local/bin/secretless-broker \
//            -test.v \
//            -test.run ^TestRunMain$$ \
//            -test.coverprofile=/test-coverage/cover.out"
//
// Normally, the Secretless Broker binary can be passed optional command line
// parameters, for example:
//
//        secretless-broker -f /secretless-test.yml -debug
//
// However, in the case of the Secretless Broker test binary, command line
// parameters are processed by the Go test infrastructure, and therefore any
// of the usual Secretless Broker command line parameters will be rejected
// and cause a test failure.
//
// To get around this limitation, the TestCoverage test will
// look for equivalent environment variable settings for the usual Secretless
// Broker command line parameters, and pass those settings to the Secretless
// Broker code. These environment variable settings include:
//
//       Environment Variable      Equivalent Command Line Parameter
//       --------------------      ---------------------------------
//       SB_CONFIG_FILE            -f <config-file>
//       SB_PROFILING_MODE         -profile [cpu|memory]
//       SB_DEBUG_ENABLED          -debug
//       SB_CONFIG_MANAGER         -config-mgr <config-mgr-spec>
//       SB_FS_WATCH_ENABLED       -watch
//       SB_PLUGIN_DIR             -p <plugin-directory>
//       SB_PLUGIN_CHECKSUM_FILE   -s <plugin-checksum-file>

func TestCoverage(t *testing.T) {
    params, err := getSecretlessOptions()
    assert.NoError(t, err)
    entrypoint.StartSecretless(params)
}

Connected Issue/Story

Resolves #[relevant GitHub issue(s), e.g. 76]

CyberArk internal issue link: [insert issue ID]()

Definition of Done

At least 1 todo must be completed in the sections below for the PR to be merged.

Changelog

[ ] The CHANGELOG has been updated, or
[x] This PR does not include user-facing changes and doesn't require a CHANGELOG update

Test coverage

[x] This PR includes new unit and integration tests to go with the code changes, or
[ ] The changes in this PR do not require tests

Documentation

[ ] Docs (e.g. READMEs) were updated in this PR
[ ] A follow-up issue to update official docs has been filed here: [insert issue ID]()
[x] This PR does not require updating any documentation

Behavior

[ ] This PR changes product behavior and has been reviewed by a PO, or
[ ] These changes are part of a larger initiative that will be reviewed later, or
[x] No behavior was changed with this PR

Security

[ ] Security architect has reviewed the changes in this PR,
[ ] These changes are part of a larger initiative with a separate security review, or
[x] There are no security aspects to these changes

cyberark / secretless-broker