Merge branch 'hotfix/#6935-#6358-wrong-zend-feed-atom-datetime-format'

Close #6935
Close #6358
Fixes #6647
updated test case to fit with set error self::NOT_FLOAT
#6647 #6648 - minor CS fixes (spacing)
#6647 #6648 - adding `@group` annotation referencing the open pull request
Merge branch 'hotfix/#6648-#6647-zend-i18n-validator-float-not-float-error-message' into develop

Close #6648
Close #6647
Forward port #6648
Forward port #6647