Upgrading from 5.0.x to 5.1.x

org.springframework.data.elasticsearch.annotations.Similarity was an enum class until 5.1. This enum was used in the @Field annotation to specify a similarity value. But besides the values defined by the enum, it is possible to have similarities with custom names in Elasticsearch. Therefore, the annotation property was changed from the type of the enum to a simple String. The previous enum values like Similarity.Default do still exist as String constants, so existing code will compile unmodified. Adaptions are necessary when this enum was used at other places than as a property of the @Field annotation.