Fix AddonExecutionResult monoid identity

modules/addonlib/src/main/scala/docspell/addons/AddonExecutionResult.scala

@@ -20,7 +20,7 @@ case class AddonExecutionResult(
 
 object AddonExecutionResult {
   val empty: AddonExecutionResult =
-    AddonExecutionResult(Nil, false)
+    AddonExecutionResult(Nil, pure = true)
 
   def combine(a: AddonExecutionResult, b: AddonExecutionResult): AddonExecutionResult =
     AddonExecutionResult(

modules/addonlib/src/test/scala/docspell/addons/AddonExecutorTest.scala

@@ -136,4 +136,15 @@ class AddonExecutorTest extends CatsEffectSuite with Fixtures with TestLoggingCo
       assertEquals(res.addonResults(1), AddonResult.success(testOut2))
     }
   }
+
+  test("AddonExecutionResult's monoid") {
+    assert(
+      AddonExecutionResult.executionResultMonoid
+        .combine(
+          AddonExecutionResult.empty,
+          AddonExecutionResult(Nil, true)
+        )
+        .pure
+    )
+  }
 }