Extract natural language and locale specific dates in content

Previously we just extracted dates in YYYY-MM-DD format from content
for date filterings during search.

Use dateparser to extract dates across locales and natural language

This should improve notes returned as context when chat searches
knowledge base with date filters

Fallback to regex for date parsing from content if dateparser fails

- Limit natural date extractor capabilities to improve performance
  - Assume language is english
    Language detection otherwise takes a REALLY long time
  - Do not extract unix timestamps, timezone
    - This isn't required, as just using date and approximating dates as UTC

tests/test_date_filter.py

@@ -116,7 +116,7 @@ def test_date_filter_regex():
     assert dtrange_match == []
 
 
-def test_get_file_filter_terms():
+def test_get_date_filter_terms():
     dtrange_match = DateFilter().get_filter_terms('multi word head dt>"today" dt:"1984-01-01"')
     assert dtrange_match == ["dt>'today'", "dt:'1984-01-01'"]
 
@@ -134,3 +134,29 @@ def test_get_file_filter_terms():
 
     dtrange_match = DateFilter().get_filter_terms("head tail")
     assert dtrange_match == []
+
+
+def test_date_extraction():
+    extracted_dates = DateFilter().extract_dates("")
+    assert extracted_dates == [], "Expected to handle empty string"
+
+    extracted_dates = DateFilter().extract_dates("head tail")
+    assert extracted_dates == [], "Expected to handle no dates"
+
+    extracted_dates = DateFilter().extract_dates("head CREATED: today tail")
+    assert extracted_dates == [], "Expected relative date to be ignored"
+
+    extracted_dates = DateFilter().extract_dates("head CREATED: today SCHEDULED: 1984-04-01 tail")
+    assert extracted_dates == [datetime(1984, 4, 1, 0, 0, 0)], "Expected only YMD structured date to be extracted"
+
+    extracted_dates = DateFilter().extract_dates("head CREATED: today SCHEDULED: 01-04-1984 tail")
+    assert extracted_dates == [datetime(1984, 4, 1, 0, 0, 0)], "Expected DMY structured date to be extracted"
+
+    extracted_dates = DateFilter().extract_dates("head Updates from April 1984 tail")
+    assert extracted_dates == [datetime(1984, 4, 1, 0, 0, 0)], "Expected natural date to be extracted"
+
+    extracted_dates = DateFilter().extract_dates("CLOCK: [1984-04-01 mer 09:50]--[1984-04-01 mer 10:10] => 24:20")
+    expected_dates = [datetime(1984, 4, 1, 9, 50, 0), datetime(1984, 4, 1, 10, 10, 0)]
+    assert all(
+        [dt in extracted_dates for dt in expected_dates]
+    ), "Expected multiple non-english dates extracted from logbook entry"