[typescript-rxjs]: Add support for nullable (#4438)

Author: komachi

modules/openapi-generator/src/main/resources/typescript-rxjs/apis.mustache

@@ -15,7 +15,7 @@ import {
 {{#allParams.0}}
 export interface {{operationIdCamelCase}}Request {
     {{#allParams}}
-    {{paramName}}{{^required}}?{{/required}}: {{#isEnum}}{{{datatypeWithEnum}}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{/isEnum}};
+    {{paramName}}{{^required}}?{{/required}}: {{#isEnum}}{{{datatypeWithEnum}}}{{/isEnum}}{{^isEnum}}{{{dataType}}}{{#isNullable}} | null{{/isNullable}}{{/isEnum}};
     {{/allParams}}
 }
 

modules/openapi-generator/src/main/resources/typescript-rxjs/modelGeneric.mustache

@@ -21,7 +21,7 @@ export interface {{classname}} {{#parent}}extends {{{parent}}} {{/parent}}{
      * @type {{=<% %>=}}{<%&datatype%>}<%={{ }}=%>
      * @memberof {{classname}}
      */
-    {{#isReadOnly}}readonly {{/isReadOnly}}{{name}}{{^required}}?{{/required}}: {{#isEnum}}{{{datatypeWithEnum}}}{{/isEnum}}{{^isEnum}}{{{datatype}}}{{/isEnum}};
+    {{#isReadOnly}}readonly {{/isReadOnly}}{{name}}{{^required}}?{{/required}}: {{#isEnum}}{{{datatypeWithEnum}}}{{/isEnum}}{{^isEnum}}{{{datatype}}}{{#isNullable}} | null{{/isNullable}}{{/isEnum}};
 {{/vars}}
 }{{#hasEnums}}