Fix: repo-config for pullRequests.draft should not be wiped when combined with _unset_ config

modules/core/src/main/scala/org/scalasteward/core/repoconfig/PullRequestsConfig.scala

@@ -63,7 +63,10 @@ object PullRequestsConfig {
           grouping = x.grouping |+| y.grouping,
           includeMatchedLabels = x.includeMatchedLabels.orElse(y.includeMatchedLabels),
           customLabels = x.customLabels |+| y.customLabels,
-          draft = (x.draft, y.draft).mapN(_ || _)
+          draft = {
+            implicit val booleanOrMonoid: Monoid[Boolean] = Monoid.instance(false, _ || _)
+            x.draft |+| y.draft
+          }
         )
     )
 }

modules/core/src/test/scala/org/scalasteward/core/repoconfig/PullRequestsConfigTest.scala

@@ -1,9 +1,20 @@
 package org.scalasteward.core.repoconfig
 
+import cats.implicits.*
 import cats.kernel.laws.discipline.MonoidTests
 import munit.DisciplineSuite
 import org.scalasteward.core.TestInstances.*
 
 class PullRequestsConfigTest extends DisciplineSuite {
   checkAll("Monoid[PullRequestsConfig]", MonoidTests[PullRequestsConfig].monoid)
+
+  test("global config to use 'draft' PRs should be retained after merging with local config") {
+    val draftTrue = PullRequestsConfig(draft = Some(true))
+    val draftUnset = PullRequestsConfig()
+    val draftFalse = PullRequestsConfig(draft = Some(false))
+
+    assert((draftTrue |+| draftUnset).draft === Some(true))
+    assert((draftTrue |+| draftFalse).draft === Some(true))
+    assert((draftUnset |+| draftUnset).draft === None)
+  }
 }