Clarify ordering of auth schemes in ServiceIndex

Updates the docs for getEffectiveAuthSchemes to clarify that the
returned auth schemes will be in alphabetical order by shape id
if there is no `auth` trait present. This was always the case due
to the usage of TreeMap, but the documentation didn't explicitly
state it.

Tests were also updated to ensure this ordering.

smithy-model/src/main/java/software/amazon/smithy/model/knowledge/ServiceIndex.java

@@ -127,7 +127,7 @@ public Map<ShapeId, Trait> getAuthSchemes(ToShapeId service) {
      *
      * <p>The returned map is provided in the same order as the values in the
      * {@code auth} trait if an auth trait is present, otherwise the result
-     * is returned in an undefined order.
+     * returned is ordered alphabetically by absolute shape id.
      *
      * <p>An empty map is returned if {@code service} cannot be found in the
      * model or is not a service shape.
@@ -167,7 +167,7 @@ public Map<ShapeId, Trait> getEffectiveAuthSchemes(ToShapeId service) {
      *
      * <p>The returned map is provided in the same order as the values in the
      * {@code auth} trait if an auth trait is present, otherwise the result
-     * is returned in an undefined order.
+     * returned is ordered alphabetically by absolute shape id.
      *
      * <p>An empty map is returned if {@code service} shape cannot be found
      * in the model or is not a service shape. An empty map is returned if

smithy-model/src/test/java/software/amazon/smithy/model/knowledge/ServiceIndexTest.java

@@ -19,7 +19,10 @@
 import static org.hamcrest.Matchers.empty;
 import static org.hamcrest.Matchers.hasKey;
 import static org.hamcrest.Matchers.hasSize;
+import static org.hamcrest.Matchers.equalTo;
 
+import java.util.ArrayList;
+import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.AfterAll;
 import org.junit.jupiter.api.BeforeAll;
@@ -80,10 +83,11 @@ public void getsAuthSchemesOfServiceWithNoAuthTrait() {
         Map<ShapeId, Trait> auth = serviceIndex.getEffectiveAuthSchemes(
                 ShapeId.from("smithy.example#ServiceWithNoAuthTrait"));
 
-        assertThat(auth.keySet(), hasSize(3));
-        assertThat(auth, hasKey(HttpBasicAuthTrait.ID));
-        assertThat(auth, hasKey(HttpDigestAuthTrait.ID));
-        assertThat(auth, hasKey(HttpBearerAuthTrait.ID));
+        List<ShapeId> ids = new ArrayList<>(auth.keySet());
+        assertThat(ids, hasSize(3));
+        assertThat(ids.get(0), equalTo(HttpBasicAuthTrait.ID));
+        assertThat(ids.get(1), equalTo(HttpBearerAuthTrait.ID));
+        assertThat(ids.get(2), equalTo(HttpDigestAuthTrait.ID));
     }
 
     @Test
@@ -104,10 +108,11 @@ public void getsAuthSchemesOfOperationWithNoAuthTraitAndServiceWithNoAuthTrait()
                 ShapeId.from("smithy.example#ServiceWithNoAuthTrait"),
                 ShapeId.from("smithy.example#OperationWithNoAuthTrait"));
 
-        assertThat(auth.keySet(), hasSize(3));
-        assertThat(auth, hasKey(HttpBasicAuthTrait.ID));
-        assertThat(auth, hasKey(HttpDigestAuthTrait.ID));
-        assertThat(auth, hasKey(HttpBearerAuthTrait.ID));
+        List<ShapeId> ids = new ArrayList<>(auth.keySet());
+        assertThat(ids, hasSize(3));
+        assertThat(ids.get(0), equalTo(HttpBasicAuthTrait.ID));
+        assertThat(ids.get(1), equalTo(HttpBearerAuthTrait.ID));
+        assertThat(ids.get(2), equalTo(HttpDigestAuthTrait.ID));
     }
 
     @Test
@@ -117,9 +122,10 @@ public void getsAuthSchemesOfOperationWithNoAuthTraitAndServiceWithAuthTrait() {
                 ShapeId.from("smithy.example#ServiceWithAuthTrait"),
                 ShapeId.from("smithy.example#OperationWithNoAuthTrait"));
 
-        assertThat(auth.keySet(), hasSize(2));
-        assertThat(auth, hasKey(HttpBasicAuthTrait.ID));
-        assertThat(auth, hasKey(HttpDigestAuthTrait.ID));
+        List<ShapeId> ids = new ArrayList<>(auth.keySet());
+        assertThat(ids, hasSize(2));
+        assertThat(ids.get(0), equalTo(HttpBasicAuthTrait.ID));
+        assertThat(ids.get(1), equalTo(HttpDigestAuthTrait.ID));
     }
 
     @Test