fix: sample high-volume "Token required" Sentry errors at 1% (#116)

## Summary

- Adds a `before_send` hook to Sentry SDK init that samples "Token
required" error events at 1% (1 in 100), dropping the rest
- Issue [CLI-S](https://codecov.sentry.io/issues/CLI-S) has ~21M
occurrences flooding Sentry; this reduces volume while still capturing
representative samples
- The sampling pattern list (`_SAMPLED_MESSAGES`) is extensible for
future high-volume errors

## Test plan

- [ ] Verify existing tests pass (`pytest tests/helpers/test_args.py`)
- [ ] Confirm other Sentry events (non-"Token required") are unaffected
and always sent
- [ ] After deploy, monitor CLI-S event volume in Sentry to confirm ~99%
reduction

Author: thomasrockhu-codecov

codecov-cli/codecov_cli/opentelemetry.py

@@ -1,12 +1,40 @@
 import os
+import random
 
 import sentry_sdk
 
 from codecov_cli import __version__
 
+_SAMPLED_MESSAGES = [
+    "Token required",
+]
+_SAMPLE_RATE = 100
 _SKIP_TAG_KEYS = {"branch", "flags", "commit_sha", "env_vars"}
 
 
+def _before_send(event, hint):
+    messages = []
+    if "message" in event and event.get("message") is not None:
+        messages.append(event.get("message"))
+    if "logentry" in event and "message" in event.get("logentry", {}) and event.get("logentry", {}).get("message") is not None:
+        messages.append(event.get("logentry", {}).get("message"))
+    if "exception" in event and event.get("exception") is not None:
+        for exc in event.get("exception", {}).get("values", []):
+            if "value" in exc:
+                messages.append(exc.get("value"))
+
+    matched = False
+    for message in messages:
+        for pattern in _SAMPLED_MESSAGES:
+            if pattern in message:
+                matched = True
+                break
+
+    if matched and random.randint(1, _SAMPLE_RATE) != 1:
+        return None
+    return event
+
+
 def init_telem(ctx):
     if ctx["disable_telem"]:
         return
@@ -20,6 +48,7 @@ def init_telem(ctx):
         enable_tracing=True,
         environment=os.getenv("CODECOV_ENV", "production"),
         release=f"cli@{__version__}",
+        before_send=_before_send,
     )