fix(traces): reject ids with a trailing newline

`$` matches before a final newline, so the length check plus `match`
accepted a 31-hex trace id or 15-hex span id followed by `\n`. Use
`fullmatch` so the validators enforce their contract.

Author: turnipdabeets

posthog/test/tracing/test_ids.py

@@ -55,6 +55,7 @@ class TestValidation:
             ("abc", False),
             ("4BF92F3577B34DA6A3CE929D0E0E4736", False),
             ("zz" * 16, False),
+            ("a" * 31 + "\n", False),
             (12345, False),
             (None, False),
         ],
@@ -68,6 +69,7 @@ def test_is_valid_trace_id(self, value, expected):
             ("00f067aa0ba902b7", True),
             ("0" * 16, False),
             ("4bf92f3577b34da6a3ce929d0e0e4736", False),
+            ("a" * 15 + "\n", False),
         ],
     )
     def test_is_valid_span_id(self, value, expected):

posthog/tracing/_ids.py

@@ -39,7 +39,7 @@ def _is_valid_hex_id(value: object, length: int, invalid: str) -> bool:
         isinstance(value, str)
         and len(value) == length
         and value != invalid
-        and _HEX_RE.match(value) is not None
+        and _HEX_RE.fullmatch(value) is not None
     )