Merge branch '3449899-additional-mapping-saving' into '1.0.x'

...al_mappings/src/SchemaDotOrgAdditionalMappingsManager.php

...ernel/SchemaDotOrgAdditionalMappingsJsonApiKernelTest.php

.../SchemaDotOrgFieldGroupEntityDisplayBuilderKernelTest.php

...s/schemadotorg_jsonapi/src/SchemaDotOrgJsonApiManager.php

modules/schemadotorg_metatag/schemadotorg_metatag.module

src/Entity/SchemaDotOrgMapping.php

src/SchemaDotOrgMappingInterface.php

src/SchemaDotOrgMappingManager.php

src/SchemaDotOrgMappingManagerInterface.php

tests/src/Kernel/SchemaDotOrgMappingEntityKernelTest.php