Fix regular expression which matches Postgres RETURNING keyword

[resolves #377][#384]

Author: govi20

src/main/java/io/r2dbc/postgresql/util/GeneratedValuesUtils.java

@@ -29,7 +29,7 @@ public final class GeneratedValuesUtils {
 
     private static final Pattern INSERT = Pattern.compile(".*INSERT.*", CASE_INSENSITIVE | Pattern.DOTALL);
 
-    private static final Pattern RETURNING = Pattern.compile(".*RETURNING.*", CASE_INSENSITIVE | Pattern.DOTALL);
+    private static final Pattern RETURNING = Pattern.compile(".*\\bRETURNING\\b.*", CASE_INSENSITIVE | Pattern.DOTALL);
 
     private static final Pattern UPDATE = Pattern.compile(".*UPDATE.*", CASE_INSENSITIVE | Pattern.DOTALL);
 

src/test/java/io/r2dbc/postgresql/util/GeneratedValuesUtilsUnitTests.java

@@ -52,6 +52,8 @@ void augmentNoSql() {
     void hasReturning() {
         assertThat(GeneratedValuesUtils.hasReturningClause("test-sql")).isFalse();
         assertThat(GeneratedValuesUtils.hasReturningClause("test-sql RETURNING *")).isTrue();
+        assertThat(GeneratedValuesUtils.hasReturningClause("select * from userReturning")).isFalse();
+        assertThat(GeneratedValuesUtils.hasReturningClause("select * from ReturningUser")).isFalse();
     }
 
     @Test