Documentation cannot be created with Javadoc because of errors

[stweil]

Describe the bug
mvn javadoc:javadoc fails with errors after processing the first module (Kitodo-API):

[ERROR] /kitodo-production/Kitodo-API/src/main/java/org/kitodo/api/dataeditor/rulesetmanagement/MetadataViewWithValuesInterface.java:27: error: reference not found
[ERROR]  * {@link ComplexMetadataViewInterface#getSortedVisibleMetadatas(Collection, Collection)}
[ERROR]           ^
[ERROR] /kitodo-production/Kitodo-API/src/main/java/org/kitodo/api/dataformat/MediaPartial.java:32: error: reference not found
[ERROR]      *         {@link org.kitodo.production.helper.metadata.MediaPartialHelper#FORMATTED_TIME_PATTERN}
[ERROR]                       ^
[ERROR] /kitodo-production/Kitodo-API/src/main/java/org/kitodo/api/dataformat/MediaPartial.java:43: error: reference not found
[ERROR]      *         {@link org.kitodo.production.helper.metadata.MediaPartialHelper#FORMATTED_TIME_PATTERN}
[ERROR]                       ^
[ERROR] /kitodo-production/Kitodo-API/src/main/java/org/kitodo/api/dataformat/MediaPartial.java:46: error: reference not found
[ERROR]      *         {@link org.kitodo.production.helper.metadata.MediaPartialHelper#FORMATTED_TIME_PATTERN}

More errors exist in other modules.

To Reproduce
Steps to reproduce the behavior:

1. Run `mvn javadoc:javadoc
2. See error

Expected behavior
There must not be any errors because otherwise it is not possible to build the documentation.

Release
All recent releases including Git master.