v0.4.4

Making generated OPERATION_NAME public (#751)
Use value equality comparison for CacheKey.NO_KEY (#766)
Make the plugin work a pure kotlin project (#755)
Bump code gen version to 0.18.3 (#770)
Serialize custom scalar type map value to string as a json (#771)
Generate subscription operation models (#774)
Remove 153 synthetic accessors from source files. (#777)
Implement "useJavaBeansSemanticNaming" (#772)
annotate input value as nullable (#782)
Serialize custom scalar type list as json string (#784)
add OPERATION_ID as static field. (#788)
Fix issue with non optional field with inline fragment (#789)
Introduce subscription call (#780)
Escape java reserved word as enum const value (#796)
Make ApolloStoreOperation.Callback public (#798)
Serialize null values during GraphQL operation serialization (#802)
Subscription JavaDocs (#805)
Attach operation name to http headers, add operation id as call tag (#806)
Add support of multi-dimensional arrays for input types (#808)
Clear stale files, trigger re-generation on plugin configuration change (#810)
Fix issue with nested inline fragments (#812)
handle ApolloCacheHeaders.DO_NOT_STORE when merging a collection of records (#765)