[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/app/mention_parser_standard_test.go

@@ -11,6 +11,7 @@ import (
 )
 
 func TestIsKeywordMultibyte(t *testing.T) {
+	mainHelper.Parallel(t)
 	id1 := model.NewId()
 
 	for name, tc := range map[string]struct {
@@ -116,6 +117,7 @@ func TestIsKeywordMultibyte(t *testing.T) {
 }
 
 func TestCheckForMentionUsers(t *testing.T) {
+	mainHelper.Parallel(t)
 	id1 := model.NewId()
 	id2 := model.NewId()
 
@@ -213,6 +215,7 @@ func TestCheckForMentionUsers(t *testing.T) {
 }
 
 func TestCheckForMentionGroups(t *testing.T) {
+	mainHelper.Parallel(t)
 	groupID1 := model.NewId()
 	groupID2 := model.NewId()
 
@@ -279,6 +282,7 @@ func TestCheckForMentionGroups(t *testing.T) {
 }
 
 func TestProcessText(t *testing.T) {
+	mainHelper.Parallel(t)
 	userID1 := model.NewId()
 
 	groupID1 := model.NewId()