Muitilile error during generation openapi client from swagger

test-github-api.zip を展開し、test-github-api ディレクトリに移動して mvn clean install を実行し、生成されたクライアントのコンパイルエラーを再現します。生成された RepositoryCreatedAt.java、RepositoryPushedAt.java、JSON.java、および budget モデルのファイルと、それらを生成した OpenAPI スキーマを調査します。報告された生成済み Java ソースが、メソッドの欠落および ContentDirectory クラスのエラーなしでコンパイルできれば完了です。

Hi
I am generating client using openapi toolkit base on your swagger schema. I and during compilation getting multiple errors

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.11.0:compile (default-compile) on project test-github-api: Compilation failure: Compilation failure:
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryCreatedAt.java:[118,39] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryCreatedAt.java:[242,27] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryPushedAt.java:[118,39] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/RepositoryPushedAt.java:[247,27] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.time.OffsetDateTime
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/JSON.java:[79,94] cannot find symbol
[ERROR] symbol: class ContentDirectory
[ERROR] location: package api.github.com.generated.model
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/BillingUpdateBudgetOrg200ResponseBudget.java:[461,15] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/Budget.java:[397,13] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/GetBudget.java:[464,13] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] /Users/arseniy/MyPrj/git/test-github-api/target/generated-sources/openapi/src/gen/java/main/api/github/com/generated/model/BillingUpdateBudgetOrgRequest.java:[432,15] cannot find symbol
[ERROR] symbol: method validateJsonElement(com.google.gson.JsonElement)
[ERROR] location: class java.lang.String
[ERROR] -> [Help 1]

How to reproduce:

1. open zip file test-github-api.zip
2. cd test-github-api
3. mvn clean install

Thanks
Arseniy Isakov

test-github-api.zip