AbstractTypeScriptClientCodegen.java@223 returns empty string in case name = "="

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
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Description

When generating properties with a name of "=" into any of Typescript options that property disappears from generated code

Diving deeper into the code I realized its AbstractTypeScriptClientCodegen to blame and more specifically line 223 where after passing "=" to sanitizeName function, it returns an empty string. This results in the whole public String toParamName(String name) function returns empty string too, which I believe is bad behaviour.

Resulting code is invalid due to syntax issue for example:
someFunction(one: string, two: string, :string)

For pure unblocking purposes I introduced, but I believe there is a better solution to that instead

        if ("=".equals(name)) {
            name = "equals";
        }

openapi-generator version

4.2.3-SNAPSHOT (master)

OpenAPI declaration file content or url

https://gist.github.com/krizic/98db135224e4a84d07ab9ac58d91b720

Command line used for generation

java -jar openapi-generator-cli.jar generate -i full_documentation.json -g typescript-fetch -o temp
java -jar openapi-generator-cli.jar generate -i full_documentation.json -g typescript-axios -o temp

Steps to reproduce

After generating please open any of the generated APIs, typescript should already highlit all the function with invalid syntax (please ignore other errors)

Suggest a fix

AbstractTypeScriptClientCodegen.toParamName should in no case result with empty string.
Internal sanitizeName call should be changed/replaced to not turn "=" into ""

I agree that "=" seems like a poor convention for naming parameters, however, it is in this case being used by https://strapi.io/

Start in AbstractTypeScriptClientCodegen.java around line 223, then trace toParamName and its sanitizeName call. Reproduce with the provided OpenAPI declaration and the typescript-fetch or typescript-axios generation commands. Done means a property named "=" no longer disappears and the generated TypeScript has no empty parameter name or resulting syntax error.