fix custom variable quoting in sql* query interpolations

public/app/plugins/datasource/postgres/datasource.ts

@@ -16,7 +16,7 @@ export class PostgresDatasource {
   interpolateVariable(value, variable) {
     if (typeof value === 'string') {
       if (variable.multi || variable.includeAll) {
-        return "'" + value + "'";
+        return "'" + value.replace(/'/g, `''`) + "'";
       } else {
         return value;
       }
@@ -27,7 +27,7 @@ export class PostgresDatasource {
     }
 
     var quotedValues = _.map(value, function(val) {
-      return "'" + val + "'";
+      return "'" + val.replace(/'/g, `''`) + "'";
     });
     return quotedValues.join(',');
   }

public/app/plugins/datasource/postgres/specs/datasource.jest.ts

@@ -215,6 +215,13 @@ describe('PostgreSQLDatasource', function() {
       });
     });
 
+    describe('and variable contains single quote', () => {
+      it('should return a quoted value', () => {
+        ctx.variable.multi = true;
+        expect(ctx.ds.interpolateVariable("a'bc", ctx.variable)).toEqual("'a''bc'");
+      });
+    });
+
     describe('and variable allows all and is a string', () => {
       it('should return a quoted value', () => {
         ctx.variable.includeAll = true;