feat(schema): Add Schema sealed interface, BooleanSchema, AdditionalProperties wrapper

Author: thced

src/main/java/com/retailsvc/http/spec/schema/AdditionalProperties.java

@@ -0,0 +1,9 @@
+package com.retailsvc.http.spec.schema;
+
+public sealed interface AdditionalProperties {
+  record Allowed() implements AdditionalProperties {}
+
+  record Forbidden() implements AdditionalProperties {}
+
+  record SchemaConstraint(Schema schema) implements AdditionalProperties {}
+}

src/main/java/com/retailsvc/http/spec/schema/BooleanSchema.java

@@ -0,0 +1,5 @@
+package com.retailsvc.http.spec.schema;
+
+import java.util.Set;
+
+public record BooleanSchema(Set<TypeName> types) implements Schema {}

src/main/java/com/retailsvc/http/spec/schema/Schema.java

@@ -0,0 +1,7 @@
+package com.retailsvc.http.spec.schema;
+
+import java.util.Set;
+
+public sealed interface Schema permits BooleanSchema {
+  Set<TypeName> types();
+}

src/test/java/com/retailsvc/http/spec/schema/AdditionalPropertiesTest.java

@@ -0,0 +1,27 @@
+package com.retailsvc.http.spec.schema;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Set;
+import org.junit.jupiter.api.Test;
+
+class AdditionalPropertiesTest {
+  @Test
+  void allowedIsDefault() {
+    AdditionalProperties ap = new AdditionalProperties.Allowed();
+    assertThat(ap).isInstanceOf(AdditionalProperties.Allowed.class);
+  }
+
+  @Test
+  void forbiddenSentinel() {
+    assertThat(new AdditionalProperties.Forbidden())
+        .isInstanceOf(AdditionalProperties.Forbidden.class);
+  }
+
+  @Test
+  void schemaConstraintCarriesSchema() {
+    Schema inner = new BooleanSchema(Set.of(TypeName.BOOLEAN));
+    AdditionalProperties ap = new AdditionalProperties.SchemaConstraint(inner);
+    assertThat(((AdditionalProperties.SchemaConstraint) ap).schema()).isSameAs(inner);
+  }
+}