chore(cubesql): SQL push down support for IS NULL and IS NOT NULL expressions -- missing templates

Author: paveltiunov

packages/cubejs-schema-compiler/src/adapter/BaseQuery.js

@@ -2451,7 +2451,8 @@ class BaseQuery {
       },
       expressions: {
         column_aliased: '{{expr}} {{quoted_alias}}',
-        case: 'CASE {% if expr %}{{ expr }} {% endif %}{% for when, then in when_then %}WHEN {{ when }} THEN {{ then }}{% endfor %}{% if else_expr %} ELSE {{ else_expr }}{% endif %} END',
+        case: 'CASE{% if expr %}{{ expr }} {% endif %}{% for when, then in when_then %} WHEN {{ when }} THEN {{ then }}{% endfor %}{% if else_expr %} ELSE {{ else_expr }}{% endif %} END',
+        is_null: '{{ expr }} {% if negate %}NOT {% endif %}IS NULL',
         binary: '({{ left }} {{ op }} {{ right }})',
         sort: '{{ expr }} {% if asc %}ASC{% else %}DESC{% endif %}{% if nulls_first %} NULLS FIRST{% endif %}',
         cast: 'CAST({{ expr }} AS {{ data_type }})',