EZP-21700: add language code to SortClause FieldTarget
EZP-21700: add integration tests
EZP-21700: added BC note
Fixed: constructor PHPDoc  description
EZP-21700: make languageCode optional and join with main language
EZP-21700: prevent Field SortClauses with language from filtering Content by language
EZP-21700: added validation of Field SortClauses
EZP-21700: fixed: join only with published ContentType/FieldDefinition
EZP-21700: tested: join only with published ContentType/FieldDefinition
EZP-21700: use ContentTypeId instead of ContentTypeIdentifier
EZP-21700: skip Field SortClause tests with Solr storage
Merge pull request #553 from ezsystems/fix-EZP-21700-field-sort-clause-language

Fix EZP-21700: Search API returning duplicate content ids