Refactor: func StringInSlice to slices.Contains (#24262)

* Refactor: Use generic to change func StringInSlice to Contains

* Refactor: Use generic to change func stringNotInSlice to Contains

Make utils.go (dir server/public/utils) and func Contains

* Refactor: Move func Contains from channels/utils to public/utils

Move func Contains from channels/utils to public/utils

Fix import declarations line

* Docs: Add a description of the Contains function

* Test: add TestContains

Add a test code for a Contain function

server/channels/app/role.go

@@ -12,6 +12,8 @@ import (
 	"strings"
 
 	"github.com/mattermost/mattermost/server/public/model"
+	pUtils "github.com/mattermost/mattermost/server/public/utils"
+
 	"github.com/mattermost/mattermost/server/v8/channels/store"
 	"github.com/mattermost/mattermost/server/v8/channels/utils"
 )
@@ -187,13 +189,13 @@ func (a *App) UpdateRole(role *model.Role) (*model.Role, *model.AppError) {
 
 	builtInRolesMinusChannelRoles := append(utils.RemoveStringsFromSlice(model.BuiltInSchemeManagedRoleIDs, builtInChannelRoles...), model.NewSystemRoleIDs...)
 
-	if utils.StringInSlice(savedRole.Name, builtInRolesMinusChannelRoles) {
+	if pUtils.Contains(builtInRolesMinusChannelRoles, savedRole.Name) {
 		return savedRole, nil
 	}
 
 	var roleRetrievalFunc func() ([]*model.Role, *model.AppError)
 
-	if utils.StringInSlice(savedRole.Name, builtInChannelRoles) {
+	if pUtils.Contains(builtInChannelRoles, savedRole.Name) {
 		roleRetrievalFunc = func() ([]*model.Role, *model.AppError) {
 			roles, nErr := a.Srv().Store().Role().AllChannelSchemeRoles()
 			if nErr != nil {