Add API Error Handler (#74)

* Add error handler that converts from rpc.Status errors to Watchtower API errors.

* Better testing for ErrorHandler.

* Rename testcase and remove empty default switch case.

* Change the error status back to int64.

* Converting everything to int32s.

jsonpb wraps int64s as a string which we dont like.  We'll figure out how to use values larger than int64s when it comes up.

* Remove special casing for TraceId which isn't needed anymore.

* Removing wrappers from error details since we never need to know when they are set or unset from the end user.

* Using the helper error functions inside the project service.

* Correct usage of hclog, replace panic with Error log.

* Adding periods to all API returned errors, correct spelling, fix missed invalid argument error not using helper function.

* Change our logged errors to Error instead of Warn.

* Add TODO for defining and using our own defined API error codes.

* Add TODO to remove internal error messages.

api/util.go

@@ -30,15 +30,15 @@ func StringOrNil(in string) *string {
 }
 
 // Int returns the given int64 as an int64 pointer
-func Int(in int64) *int64 {
-	ret := new(int64)
+func Int(in int32) *int32 {
+	ret := new(int32)
 	*ret = in
 	return ret
 }
 
 // IntOrNil is like Int, but the returned pointer will be nil if the integer is
 // 0
-func IntOrNil(in int64) *int64 {
+func IntOrNil(in int32) *int32 {
 	if in == 0 {
 		return nil
 	}