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/scopes/project_test.go

@@ -1,6 +1,7 @@
 package scopes
 
 import (
+	"net/http"
 	"testing"
 
 	"github.com/hashicorp/watchtower/api"
@@ -43,7 +44,32 @@ func TestProjects_Crud(t *testing.T) {
 	existed, apiErr, err = org.DeleteProject(tc.Context(), p)
 	assert.NoError(t, err)
 	assert.False(t, existed, "Expected project to not exist when deleted, but it did.")
-
-	// TODO: Error conditions once the proper errors are being returned.
-	// Probably as parallel subtests against the same DB.
+}
+
+// TODO: Get better coverage for expected errors and error formats.
+func TestProject_Errors(t *testing.T) {
+	assert := assert.New(t)
+	tc := controller.NewTestController(t, nil)
+	defer tc.Shutdown()
+	ctx := tc.Context()
+
+	client := tc.Client()
+	org := &Organization{
+		Client: client,
+	}
+	createdProj, apiErr, err := org.CreateProject(ctx, &Project{})
+	assert.NoError(err)
+	assert.NotNil(createdProj)
+	assert.Nil(apiErr)
+
+	_, apiErr, err = org.ReadProject(ctx, &Project{Id: "p_doesntexis"})
+	assert.NoError(err)
+	// TODO: Should this be nil instead of just a Project that has no values set
+	assert.NotNil(apiErr)
+	assert.EqualValues(*apiErr.Status, http.StatusNotFound)
+
+	_, apiErr, err = org.ReadProject(ctx, &Project{Id: "invalid id"})
+	assert.NoError(err)
+	assert.NotNil(apiErr)
+	assert.EqualValues(*apiErr.Status, http.StatusBadRequest)
 }