* chore(backend): tidy go.mod and update tools.go
* go install, instead of go get
* fix problems reported by go vet
* simplify some ide reported redundant syntax
* license is not required for generated code
* remove licenses for generated code
* cleanup
* remove license more
* rm unused BUILD.bazel files
* fixed generate_api.sh
* reimport error.proto
* Use Bazel to build the entire backend.
This also uses Bazel to generate code from the API definition in the
proto files.
The Makefile is replaced with a script that uses Bazel to first generate
the code, and then copy them back into the source tree.
Most of the BUILD files were generated automatically using Gazelle.
* Fix indentation in generate_api.sh
* Clean up WORKSPACE
* Add README for building/testing backend.
Also fix the missing licenses in the generated proto files.
* Add license to files under go_http_client