huge refactoring

app/handlers/http/errors.go

@@ -0,0 +1,15 @@
+package http
+
+import "fmt"
+
+type notAuthorizedContentTypeError struct{}
+
+func (e *notAuthorizedContentTypeError) Error() string {
+	return fmt.Sprintf("Accepted values for 'Content-Type': %s, %s, %s, %s", PDFContentType, HTMLContentType, OctetStreamContentType, MultipartFormDataContentType)
+}
+
+type notAuthorizedFileContentTypeError struct{}
+
+func (e *notAuthorizedFileContentTypeError) Error() string {
+	return fmt.Sprintf("Unable to detect a file 'Content-Type'")
+}