Auto-detect invalid casing linting issues

From #607, it appears invalid casing (`Id` instead of `ID`) linting issues are not being reported by our golangci-lint configuration.

## Expected solution

If an invalid casing is detected, such as:

```
type Foo struct {
  Id string
}
```

Then, the linter should error and require the casing to be fixed:

```
type Foo struct {
  ID string
}
```