fix(grammar): Support CONSTRAINTS keyword in inline and out-of-line constraints as an alternative to CONSTRAINT

Although it seems that this syntax has never been documented in the last 20 years in Oracle docs and causes parsing errors in Oracle SQL Developer, testing shows that it is still accepted by the Oracle 23.5 compiler.

Ref:
https://docs.oracle.com/cd/A87860_01/doc/server.817/a85397/state14a.htm (Oracle 8i docs)
https://docs.oracle.com/en/database/oracle/oracle-database/23/sqlrf/constraint.html (Oracle 23ai docs)
Based on debezium/debezium#5612

Author: felipebz

zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/DdlGrammar.kt

@@ -118,7 +118,7 @@ enum class DdlGrammar : GrammarRuleKey {
             )
 
             b.rule(INLINE_CONSTRAINT).define(
-                b.optional(CONSTRAINT, IDENTIFIER_NAME),
+                b.optional(b.firstOf(CONSTRAINT, CONSTRAINTS), IDENTIFIER_NAME),
                 b.firstOf(
                     b.sequence(
                         b.firstOf(
@@ -160,7 +160,7 @@ enum class DdlGrammar : GrammarRuleKey {
                     b.zeroOrMore(INLINE_CONSTRAINT))
 
             b.rule(OUT_OF_LINE_CONSTRAINT).define(
-                b.optional(CONSTRAINT, IDENTIFIER_NAME),
+                b.optional(b.firstOf(CONSTRAINT, CONSTRAINTS), IDENTIFIER_NAME),
                 b.firstOf(
                     b.sequence(
                         b.firstOf(

zpa-core/src/main/kotlin/org/sonar/plugins/plsqlopen/api/PlSqlKeyword.kt

@@ -170,6 +170,7 @@ enum class PlSqlKeyword(override val value: String, val isReserved: Boolean = fa
     CONNECT_BY_ROOT("connect_by_root"),
     CONSTANT("constant"),
     CONSTRAINT("constraint"),
+    CONSTRAINTS("constraints"),
     CONSTRUCTOR("constructor"),
     CONTAINER("container"),
     CONTENT("content"),

zpa-core/src/test/kotlin/org/sonar/plugins/plsqlopen/api/ddl/InlineConstraintTest.kt

@@ -87,6 +87,7 @@ class InlineConstraintTest : RuleTest() {
     @Test
     fun matchesConstraintWithName() {
         assertThat(p).matches("constraint pk primary key")
+        assertThat(p).matches("constraints pk primary key")
     }
 
     @Test

zpa-core/src/test/kotlin/org/sonar/plugins/plsqlopen/api/ddl/OutOfLineConstraintTest.kt

@@ -72,6 +72,7 @@ class OutOfLineConstraintTest : RuleTest() {
     @Test
     fun matchesConstraintWithName() {
         assertThat(p).matches("constraint pk primary key (foo)")
+        assertThat(p).matches("constraints pk primary key (foo)")
     }
 
     @Test