🎨 Db_index for preprint

Signed-off-by: zethson <[email protected]>

ourprojects/models.py

@@ -145,7 +145,7 @@ class Meta(Record.Meta, TracksRun.Meta, TracksUpdates.Meta):
         ],
     )
     """Digital Object Identifier (DOI) for the reference."""
-    preprint: bool = BooleanField(default=False)
+    preprint: bool = BooleanField(default=False, db_index=True)
     """Whether the reference is from a preprint."""
     journal: str | None = TextField(null=True)
     """Name of the journal."""