fix: validate search when datetime is none

Author: gadomski

Diff for: stac_pydantic/api/search.py

@@ -98,8 +98,10 @@ def validate_bbox(cls, v: BBox) -> BBox:
 
     @field_validator("datetime")
     @classmethod
-    def validate_datetime(cls, value: str) -> str:
+    def validate_datetime(cls, value: Optional[str]) -> Optional[str]:
         # Split on "/" and replace no value or ".." with None
+        if value is None:
+            return value
         values = [v if v and v != ".." else None for v in value.split("/")]
 
         # If there are more than 2 dates, it's invalid

Diff for: tests/api/test_search.py

@@ -149,3 +149,7 @@ def test_search_geometry_bbox():
 def test_search_invalid_bbox(bbox):
     with pytest.raises(ValidationError):
         Search(collections=["foo"], bbox=bbox)
+
+
+def test_search_none_datetime() -> None:
+    Search(datetime=None)