The thumbnails service is now a stateless image resizer; remove everything
the old gRPC-based pipeline needed:
- proto definitions and generated code (service + messages)
- gRPC server, handler and decorators
- JWT transfer token code and the /data HTTP download endpoint
- filesystem storage layer and source fetchers (webdav + CS3 imgsource)
- duplicated encoding/generator/processor/resolution utilities
- the preprocessor packages moved to webdav in the previous commit
- dead config fields (Thumbnail struct, GRPC config, unused go-micro client),
no-op metrics/instrumentation wrappers, errors package, stale testdata and
the Makefile protobuf target
Also remove the now-meaningless thumbnails transfer secret generation from
opencloud init and point the graph service at the new webdav thumbnail
package. The README is rewritten to document the imagor-like push endpoint.
Jörn Friedrich Dreyer
efb1c648dc