add test for translation

tests/test_libretranslate.py

+from configparser import ConfigParser
+import json
+import requests
+from functools import cache
+import protocol_translation.translation as translation
+
+
+def init():
+    api_keys = ConfigParser()
+    api_keys.read("api_keys.conf")
+
+    t = LibreTranslate("https://translate.fem-net.de",
+                       api_keys["libretranslate_key"])
+
+    return t
+
+
+def test_translate():
+    t = init()
+    text_de = "Dies ist ein Ball."
+    text_en = "this is a ball."
+    assert t.translate(text_de, "de", "en") == text_en
+
+
+def test_translate_empty():
+    t = init()
+    text_de = ""
+    text_en = ""
+    assert t.translate(text_de, "de", "en") == text_en