1. use [staticcheck](https://staticcheck.io/) to check the code, and fix some issues.
2. use `go fmt` to format the code.
3. use `go mod tidy` clean the go mod.
Notable refactoring:
- Use stdlib "context" in place of "golang.org/x/net/context"
- Go-kit no longer wraps errors, so we remove the unwrap in transport_error.go
- Use MakeHandler when setting up endpoint tests (fixes test bug caught during
this refactoring)
Closes#1411.
* Change email functionality
* Code review changes for @groob
* Name change per @groob
* Code review changes per @marpaia
Also added addition non-happy path tests to satisfy concerns by @groob
