v0.2.1 * fat JAR: trim size down from 100 to 40 MB, by excluding mg4j * webgraph.py: improve logging by adding explicit start/end timings * app.py: fix wrong invocation of node_of_pid in /walk * REST server: preliminary support for HEAD requests * REST server: validate all query parameters and refactor validators * REST server: add validation for PID parameters * REST API doc: document /count method variants * REST API doc: update to match current aiohttp implementation * app.py: inline MIME types, they are single use anyway * REST server: set content-type to text or ndjson where appropriate * CLI: add "swh graph map lookup" to lookup values in binary maps * backend.py: log which JAR is being used and warn if multiple ones exist * doc: stop building javadoc for now, as we do not ship it anyway * doc: integrate git2graph doc into top-level doc and toc * git2graph doc: explain why only HEAD is supported among symbolic refs * git2graph: update doc and benchmark to use zstd * javadoc: fix docstring syntax error in NodeTypesMap * Makefile: add convenience target "java-doc" * doc: update docker-related documentation and scripts