[MM-62408] Server Code Coverage with Fully Parallel Tests (#30078)

* TestPool

* Store infra

* Store tests updates

* Bump maximum concurrent postgres connections

* More infra

* channels/jobs

* channels/app

* channels/api4

* Protect i18n from concurrent access

* Replace some use of os.Setenv

* Remove debug

* Lint fixes

* Fix more linting

* Fix test

* Remove use of Setenv in drafts tests

* Fix flaky TestWebHubCloseConnOnDBFail

* Fix merge

* [MM-62408] Add CI job to generate test coverage (#30284)

* Add CI job to generate test coverage

* Remove use of Setenv in drafts tests

* Fix flaky TestWebHubCloseConnOnDBFail

* Fix more Setenv usage

* Fix more potential flakyness

* Remove parallelism from flaky test

* Remove conflicting env var

* Fix

* Disable parallelism

* Test atomic covermode

* Disable parallelism

* Enable parallelism

* Add upload coverage step

* Fix codecov.yml

* Add codecov.yml

* Remove redundant workspace field

* Add Parallel() util methods and refactor

* Fix formatting

* More formatting fixes

* Fix reporting

server/channels/api4/main_test.go

@@ -5,8 +5,11 @@ package api4
 
 import (
 	"flag"
+	"os"
+	"strconv"
 	"testing"
 
+	"github.com/mattermost/mattermost/server/public/shared/mlog"
 	"github.com/mattermost/mattermost/server/v8/channels/testlib"
 )
 
@@ -18,10 +21,21 @@ func TestMain(m *testing.M) {
 		flag.Parse()
 	}
 
-	var options = testlib.HelperOptions{
+	var parallelism int
+	if f := flag.Lookup("test.parallel"); f != nil {
+		parallelism, _ = strconv.Atoi(f.Value.String())
+	}
+	runParallel := os.Getenv("ENABLE_FULLY_PARALLEL_TESTS") == "true" && parallelism > 1
+	if runParallel {
+		mlog.Info("Fully parallel tests enabled", mlog.Int("parallelism", parallelism))
+	}
+
+	options := testlib.HelperOptions{
 		EnableStore:     true,
 		EnableResources: true,
 		WithReadReplica: replicaFlag,
+		RunParallel:     runParallel,
+		Parallelism:     parallelism,
 	}
 
 	mainHelper = testlib.NewMainHelperWithOptions(&options)