Add variants of Get functions with existence checks

Currently, a translation that doesn't exist just defaults to the
passed message ID.

It can be helpful to be able to catch these missing cases e.g. to
save to a log.

This PR implements variants ending in 'E' like GetE, GetNE.

This wasn't implemented at the package-level scope, because for
quick translations like that the extra flexibility probably isn't
needed.

translation.go

@@ -50,3 +50,29 @@ func (t *Translation) GetN(n int) string {
 	// Return untranslated plural by default
 	return t.PluralID
 }
+
+// Get returns the string of the translation. The second return value is true
+// iff the string was found.
+func (t *Translation) GetE() (string, bool) {
+	// Look for Translation index 0
+	if _, ok := t.Trs[0]; ok {
+		if t.Trs[0] != "" {
+			return t.Trs[0], true
+		}
+	}
+
+	return "", false
+}
+
+// GetN returns the string of the plural translation. The second return value
+// is true iff the string was found.
+func (t *Translation) GetNE(n int) (string, bool) {
+	// Look for Translation index
+	if _, ok := t.Trs[n]; ok {
+		if t.Trs[n] != "" {
+			return t.Trs[n], true
+		}
+	}
+
+	return "", false
+}