✨(backend) add util to extract text from Ydoc content

Documents content is stored in the Ydoc format. We need a util
to extract it as xml/text.

src/backend/core/tests/test_utils.py

@@ -0,0 +1,37 @@
+"""Test util base64_yjs_to_text."""
+
+from core import utils
+
+# This base64 string is an example of what is saved in the database.
+# This base64 is generated from the blocknote editor, it contains
+# the text \n# *Hello* \n- w**or**ld
+TEST_BASE64_STRING = (
+    "AR717vLVDgAHAQ5kb2N1bWVudC1zdG9yZQMKYmxvY2tHcm91cAcA9e7y1Q4AAw5ibG9ja0NvbnRh"
+    "aW5lcgcA9e7y1Q4BAwdoZWFkaW5nBwD17vLVDgIGBgD17vLVDgMGaXRhbGljAnt9hPXu8tUOBAVI"
+    "ZWxsb4b17vLVDgkGaXRhbGljBG51bGwoAPXu8tUOAg10ZXh0QWxpZ25tZW50AXcEbGVmdCgA9e7y"
+    "1Q4CBWxldmVsAX0BKAD17vLVDgECaWQBdyQwNGQ2MjM0MS04MzI2LTQyMzYtYTA4My00ODdlMjZm"
+    "YWQyMzAoAPXu8tUOAQl0ZXh0Q29sb3IBdwdkZWZhdWx0KAD17vLVDgEPYmFja2dyb3VuZENvbG9y"
+    "AXcHZGVmYXVsdIf17vLVDgEDDmJsb2NrQ29udGFpbmVyBwD17vLVDhADDmJ1bGxldExpc3RJdGVt"
+    "BwD17vLVDhEGBAD17vLVDhIBd4b17vLVDhMEYm9sZAJ7fYT17vLVDhQCb3KG9e7y1Q4WBGJvbGQE"
+    "bnVsbIT17vLVDhcCbGQoAPXu8tUOEQ10ZXh0QWxpZ25tZW50AXcEbGVmdCgA9e7y1Q4QAmlkAXck"
+    "ZDM1MWUwNjgtM2U1NS00MjI2LThlYTUtYWJiMjYzMTk4ZTJhKAD17vLVDhAJdGV4dENvbG9yAXcH"
+    "ZGVmYXVsdCgA9e7y1Q4QD2JhY2tncm91bmRDb2xvcgF3B2RlZmF1bHSH9e7y1Q4QAw5ibG9ja0Nv"
+    "bnRhaW5lcgcA9e7y1Q4eAwlwYXJhZ3JhcGgoAPXu8tUOHw10ZXh0QWxpZ25tZW50AXcEbGVmdCgA"
+    "9e7y1Q4eAmlkAXckODk3MDBjMDctZTBlMS00ZmUwLWFjYTItODQ5MzIwOWE3ZTQyKAD17vLVDh4J"
+    "dGV4dENvbG9yAXcHZGVmYXVsdCgA9e7y1Q4eD2JhY2tncm91bmRDb2xvcgF3B2RlZmF1bHQA"
+)
+
+
+def test_utils_base64_yjs_to_text():
+    """Test extract text from saved yjs document"""
+    assert utils.base64_yjs_to_text(TEST_BASE64_STRING) == "Hello world"
+
+
+def test_utils_base64_yjs_to_xml():
+    """Test extract xml from saved yjs document"""
+    content = utils.base64_yjs_to_xml(TEST_BASE64_STRING)
+    assert (
+        '<heading "level"="1" "textAlignment"="left">Hello</heading>' in content
+        or '<heading "textAlignment"="left" "level"="1">Hello</heading>' in content
+    )
+    assert '<bulletListItem "textAlignment"="left">world</bulletListItem>' in content