fix: add tombstone exception mechanism

Author: supervacuus

sentry-android-core/src/main/java/io/sentry/android/core/internal/tombstone/NativeExceptionMechanism.java

@@ -0,0 +1,21 @@
+package io.sentry.android.core.internal.tombstone;
+
+import androidx.annotation.NonNull;
+
+/** Mechanism types for native crashes. */
+public enum NativeExceptionMechanism {
+  TOMBSTONE("tombstone"),
+  SIGNAL_HANDLER("signalhandler"),
+  TOMBSTONE_MERGED("tombstone_merged");
+
+  private final @NonNull String value;
+
+  NativeExceptionMechanism(@NonNull final String value) {
+    this.value = value;
+  }
+
+  @NonNull
+  public String getValue() {
+    return value;
+  }
+}

sentry-android-core/src/main/java/io/sentry/android/core/internal/tombstone/TombstoneParser.java

@@ -142,9 +142,7 @@ private static Mechanism createMechanismFromSignalInfo(
       @NonNull final TombstoneProtos.Signal signalInfo) {
 
     final Mechanism mechanism = new Mechanism();
-    // this follows the current processing triggers strictly, changing any of these
-    // alters grouping and name (long-term we might want to have a tombstone mechanism)
-    mechanism.setType("signalhandler");
+    mechanism.setType(NativeExceptionMechanism.TOMBSTONE.getValue());
     mechanism.setHandled(false);
     mechanism.setSynthetic(true);
 

sentry-android-core/src/test/java/io/sentry/android/core/internal/tombstone/TombstoneParserTest.kt

@@ -72,7 +72,7 @@ class TombstoneParserTest {
     assertNotNull(crashedThreadId)
 
     val mechanism = exception.mechanism
-    assertEquals("signalhandler", mechanism!!.type)
+    assertEquals("tombstone", mechanism!!.type)
     assertEquals(false, mechanism.isHandled)
     assertEquals(true, mechanism.synthetic)
     assertEquals("SIGSEGV", mechanism.meta!!["name"])