10 files declare their use of MessageTemplate in Message 8

DaysTest.php in tests/src/Kernel/Plugin/MessagePurge/DaysTest.php

message.module in ./message.module

API functions to manipulate messages.

MessageCron.php in tests/src/Functional/MessageCron.php

MessageTemplateCreateTrait.php in tests/src/Kernel/MessageTemplateCreateTrait.php

MessageTemplateDependenciesTest.php in tests/src/Kernel/MessageTemplateDependenciesTest.php

MessageTemplateMultipleTextField.php in src/FormElement/MessageTemplateMultipleTextField.php

MessageTemplateTest.php in tests/src/Unit/Entity/MessageTemplateTest.php

MessageTemplateUiTest.php in tests/src/Functional/MessageTemplateUiTest.php

MessageTestBase.php in tests/src/Functional/MessageTestBase.php

QuotaTest.php in tests/src/Kernel/Plugin/MessagePurge/QuotaTest.php