fix(tracing_utils): handle baggage values containing '=' in from_incoming_header (#6450)

## What's broken

`Baggage.from_incoming_header` silently drops any sentry baggage item
whose value contains an `=` character (e.g. base64-encoded strings like
`v1.0==1`). A header like
`sentry-release=v1.0==1,sentry-trace_id=abc123` produces `{'trace_id':
'abc123'}` instead of `{'release': 'v1.0==1', 'trace_id': 'abc123'}`.

## Why it happens

`key, val = item.split("=")` without a `maxsplit` argument raises
`ValueError: too many values to unpack` when the value contains `=`. The
surrounding `capture_internal_exceptions()` swallows the exception,
silently discarding the item.

## Fix

Changed `item.split("=")` to `item.split("=", 1)` so the split stops
after the first delimiter, correctly assigning the key and the full
value (including any `=` in the value).

## Test

Added `test_baggage_from_incoming_header_value_with_equals_sign` which
parses a header containing a sentry item with `==` in its value and
asserts both items are present in `sentry_items`.

Fixes #6449

Co-authored-by: Aegis Dev <devteamaegis@users.noreply.github.com>
Co-authored-by: Ivana Kellyer <ivana.kellyer@sentry.io>

Author: devteamaegis

sentry_sdk/tracing_utils.py

@@ -719,7 +719,7 @@ def from_incoming_header(
 
                 with capture_internal_exceptions():
                     item = item.strip()
-                    key, val = item.split("=")
+                    key, val = item.split("=", 1)
                     if Baggage.SENTRY_PREFIX_REGEX.match(key):
                         baggage_key = unquote(key.split("-")[1])
                         sentry_items[baggage_key] = unquote(val)

tests/test_tracing_utils.py

@@ -279,3 +279,10 @@ def test_should_continue_trace(
 
     baggage = Baggage.from_incoming_header(baggage_header) if baggage_header else None
     assert _should_continue_trace(baggage) == should_continue_trace
+
+
+def test_baggage_from_incoming_header_value_with_equals_sign():
+    # Baggage values that legitimately contain '=' (e.g. base64) must not be dropped
+    header = "sentry-release=v1.0==1,sentry-trace_id=abc123"
+    baggage = Baggage.from_incoming_header(header)
+    assert baggage.sentry_items == {"release": "v1.0==1", "trace_id": "abc123"}