Add key to each model field

Add a `[@key "someField"]` annotation to each model field, to avoid mismatches when the JSON field is not in snake_case.

Closes OpenAPITools#20765

Author: sir4ur0n

modules/openapi-generator/src/main/resources/ocaml/model.mustache

@@ -16,10 +16,10 @@ type t = {
     (* {{{.}}} *)
     {{/description}}
     {{#isEnum}}
-    {{{name}}}: {{^isMap}}Enums.{{/isMap}}{{{datatypeWithEnum}}}{{^isContainer}}{{#required}}{{#defaultValue}}[@default {{{.}}}]{{/defaultValue}}{{/required}}{{/isContainer}}{{^isContainer}}{{#required}}{{#isNullable}} option [@default {{#defaultValue}}Some({{{.}}}){{/defaultValue}}{{^defaultValue}}None{{/defaultValue}}]{{/isNullable}}{{/required}}{{/isContainer}}{{^isContainer}}{{^required}} option [@default {{#defaultValue}}Some({{{.}}}){{/defaultValue}}{{^defaultValue}}None{{/defaultValue}}]{{/required}}{{/isContainer}};
+    {{{name}}}: {{^isMap}}Enums.{{/isMap}}{{{datatypeWithEnum}}}{{^isContainer}}{{#required}}{{#defaultValue}}[@default {{{.}}}]{{/defaultValue}}{{/required}}{{/isContainer}}{{^isContainer}}{{#required}}{{#isNullable}} option [@default {{#defaultValue}}Some({{{.}}}){{/defaultValue}}{{^defaultValue}}None{{/defaultValue}}]{{/isNullable}}{{/required}}{{/isContainer}}{{^isContainer}}{{^required}} option [@default {{#defaultValue}}Some({{{.}}}){{/defaultValue}}{{^defaultValue}}None{{/defaultValue}}]{{/required}}{{/isContainer}}; [@key "{{{baseName}}}"]
     {{/isEnum}}
     {{^isEnum}}
-    {{{name}}}: {{{datatypeWithEnum}}}{{^isContainer}}{{#required}}{{#isNullable}} option{{/isNullable}}{{/required}}{{/isContainer}}{{^isContainer}}{{^required}} option [@default None]{{/required}}{{/isContainer}};
+    {{{name}}}: {{{datatypeWithEnum}}}{{^isContainer}}{{#required}}{{#isNullable}} option{{/isNullable}}{{/required}}{{/isContainer}}{{^isContainer}}{{^required}} option [@default None]{{/required}}{{/isContainer}}; [@key "{{{baseName}}}"]
     {{/isEnum}}
 {{/vars}}
 } [@@deriving yojson { strict = false }, show ];;