[BUG] Multiple OAuth files are being generated for Java clients

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• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
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Description

As shown below, multiple OAuth-related files are generated for the Java clients:

[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuth.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/src/main/java/org/openapitools/client/auth/OAuthFlow.java
[main] INFO  o.o.codegen.AbstractGenerator - writing file /tmp/javaoneof3/.openapi-generator/VERSION

openapi-generator version

latest master

OpenAPI declaration file content or url

https://raw.githubusercontent.com/CiscoM31/intersight-openapi/master/intersight-openapi-v3.yaml

Command line used for generation

java -jar modules/openapi-generator-cli/target/openapi-generator-cli.jar generate -g java --library jersey2 -i https://raw.githubusercontent.com/CiscoM31/intersight-openapi/master/intersight-openapi-v3.yaml -o /tmp/javaoneof3 --skip-validate-spec

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