[BUG][Spring] Dollar camelCase create invalid value

Created by: Zomzog

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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)?
• Have you tested with the latest master to confirm the issue still exists?
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• What's the actual output vs expected output?
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Description

When a property starts with a $ the generator will uppercase the 2nd letter.

It wiil generate

  public String get$Name() {
    return $name;
  }

  public void set$Name(String $name) {
    this.$name = $name;
  }

Jackson take it as another property and create json like this:

{
  "$name": "name",
  "$Name": "name"
}

The expected generation is

  public String get$name() {
    return $name;
  }

  public void set$name(String $name) {
    this.$name = $name;
  }

openapi-generator version

6.0.1

OpenAPI declaration file content or url