Make KEY a context-aware keyword to close #2227 (#2387)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mathiasrw <1063454+mathiasrw@users.noreply.github.com>
Co-authored-by: M. Wulff <m@rawu.dk>

Author: Copilot

src/alasqlparser.jison

@@ -359,6 +359,8 @@ Literal
 		}
 	| BRALITERAL
 		{ $$ = doubleq($1.substr(1,$1.length-2)); }
+	| KEY
+		{ $$ = $1.toLowerCase(); }
 	| error NonReserved
 		{ $$ = $2.toLowerCase() }
 	;
@@ -2131,8 +2133,8 @@ UniqueKey
 	;
 
 IndexKey
-	: INDEX Literal LPAR ColumnsList RPAR
-	| KEY Literal LPAR ColumnsList RPAR
+	: INDEX Literal LPAR ColsList RPAR
+		{ $$ = {type: 'INDEX', indexid: $2, columns: $4}; }
 	;
 ColsList
 	: Literal