Generating source code from Confluence's Open API spec produces invalid source code

Issue Summary

Using Confluence's Open API (aka "swagger") spec to generate a client (e.g. in Java) as explained in the blog post Generating a Java REST Client for Confluence Cloud does not produce working code. There seem to be various errors and missing types in the spec.

Note: there are a couple of bugs in swagger-codegen 3.0.27 that interact badly with Confluence. Using a newer version overcomes these errors.

Steps to Reproduce

1. Download a copy of Confluence open API spec:  https://developer.atlassian.com/cloud/confluence/swagger.v3.json
2. Use a tool like swagger-codegen to generate the Java client (e.g. "swagger-codegen -i swagger.v3.json -l java -o .")

Expected Results

The generated code works 

Actual Results

The generated code doesn't work due to various errors and missing types in the spec including (but not limited to):

• ContentBody is missing the type ContentBodyExpandable
• Content is missing the type Map
• ContentBody.getValue() is missing
• GenericLinks type in the spec is missing all the fields (For example, the links for next when doing a paged query, etc)
  etc.

There are also issues with `additionalProperties: true`, but these might be due to bugs in swagger-codegen: https://github.com/swagger-api/swagger-codegen/issues/5187

Workaround

Currently there is no known workaround for this behavior. A workaround will be added here when available