errors: rewrite errors to follow go best practices

Errors should not start capitalised and they should not contain the word error
or state that they "failed" as we already know it is an error

Signed-off-by: Kristoffer Dalby <kristoffer@dalby.cc>

hscontrol/db/text_serialiser.go

@@ -24,7 +24,7 @@ func maybeInstantiatePtr(rv reflect.Value) {
 }
 
 func decodingError(name string, err error) error {
-	return fmt.Errorf("error decoding to %s: %w", name, err)
+	return fmt.Errorf("decoding to %s: %w", name, err)
 }
 
 // TextSerialiser implements the Serialiser interface for fields that
@@ -48,7 +48,7 @@ func (TextSerialiser) Scan(ctx context.Context, field *schema.Field, dst reflect
 		case string:
 			bytes = []byte(v)
 		default:
-			return fmt.Errorf("failed to unmarshal text value: %#v", dbValue)
+			return fmt.Errorf("unmarshalling text value: %#v", dbValue)
 		}
 
 		if isTextUnmarshaler(fieldValue) {