feat(native): update before_send docs (#13984)

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## DESCRIBE YOUR PR
Fixes getsentry/sentry-native#1268

We fix some ancient docs which wrongly state that `before_send` uses the
`hint` parameter in the Native SDK, by cleaning up the unnecessary
'Event Hints' section.

We move the example snippet into the corresponding `before_send` and
`on_crash` sections, better showcasing how to use the passed-in values.

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Author: JoshuaMoelans

docs/platforms/native/common/configuration/filtering.mdx

@@ -22,17 +22,6 @@ All Sentry SDKs support the <PlatformIdentifier name="before-send" /> callback m
 
 Note also that breadcrumbs can be filtered, as discussed in [our Breadcrumbs documentation](/product/error-monitoring/breadcrumbs/).
 
-#### Event Hints
-
-The <PlatformIdentifier name="before-send" /> callback is passed both the `event` and a second argument, `hint`, that holds one or more hints.
-
-Typically, a `hint` holds the original exception so that additional data can be extracted or grouping is affected. In this example, the fingerprint is forced to a common value if an exception of a certain type has been caught:
-
-<PlatformContent includePath="configuration/before-send-hint" />
-
-When the SDK creates an event or breadcrumb for transmission, that transmission is typically created from some sort of source object. For instance, an error event is typically created from a log record or exception instance. For better customization, SDKs send these objects to certain callbacks (<PlatformIdentifier name="before-send" />, <PlatformIdentifier name="before-breadcrumb" /> or the event processor system in the SDK).
-
-
 ## Filtering Transaction Events
 
 To prevent certain transactions from being reported to Sentry, use the <PlatformIdentifier name="traces-sampler" /> or <PlatformIdentifier name="before-send-transaction" /> configuration option, which allows you to provide a function to evaluate the current transaction and drop it if it's not one you want.

platform-includes/configuration/before-send-hint/native.mdx

@@ -1,14 +1,29 @@
 ```c
 #include <sentry.h>
 
-sentry_value_t strip_sensitive_data(sentry_value_t event, void *hint) {
-  /* modify event here or return NULL to discard the event */
-  return event;
+sentry_value_t strip_sensitive_data(sentry_value_t event, void *hint, void *user_data) {
+    (void)hint; // unlike in other SDKs, `hint` currently contains no data.
+    // to get more crash context into a callback, use the `on_crash` hook instead.
+
+    if (strcmp(sentry_value_as_string(sentry_value_get_by_key(event, "level")), "info") == 0) {
+        // remove the user data from "info" level events
+        sentry_value_remove_by_key(event, "user");
+        // make our mark on the event
+        sentry_value_t tags = sentry_value_get_by_key(event, "tags");
+        if (!sentry_value_is_null(tags)) {
+            sentry_value_set_by_key(tags, "info", sentry_value_new_string((char*) user_data));
+        }
+    }
+
+    // return the modified event, or discard it by freeing it and returning `null`
+    //       sentry_value_decref(event);
+    //       return sentry_value_new_null();
+    return event;
 }
 
 int main(void) {
   sentry_options_t *options = sentry_options_new();
-  sentry_options_set_before_send(options, strip_sensitive_data, NULL);
+  sentry_options_set_before_send(options, strip_sensitive_data, "anonymized");
   sentry_init(options);
 
   /* ... */
@@ -25,14 +40,17 @@ The `before_send` callback implementation in `sentry-native` makes it hard to di
 #include <sentry.h>
 
 static sentry_value_t
-crash_cleanup(
+on_crash_callback(
     const sentry_ucontext_t *uctx, // provides the user-space context of the crash
-    sentry_value_t event,          // used the same way as in `before_send`
-    void *closure                  // user-data that you can provide at configuration time
+    sentry_value_t event,          // used the same way as in `before_send`; mostly empty for minidump-generating backends (crashpad, breakpad)
+    void *user_data                // user-data that you can provide at configuration time
 )
 {
-    // Do contextual clean-up before the crash is sent to sentry's backend infrastructure
-
+    // Enrich an event before the crash is sent to sentry's backend infrastructure
+    sentry_value_t tags = sentry_value_get_by_key(event, "tags");
+    if (!sentry_value_is_null(tags)) {
+        sentry_value_set_by_key(tags, "crash_hook", sentry_value_new_string("invoked"));
+    }
     /* ... */
 
     // tell the backend to retain the event (+ dump)
@@ -44,7 +62,7 @@ crash_cleanup(
 
 int main(void) {
   sentry_options_t *options = sentry_options_new();
-  sentry_options_set_on_crash(options, crash_cleanup, NULL);
+  sentry_options_set_on_crash(options, on_crash_callback, NULL);
   sentry_init(options);
 
   /* ... */