[BUG][Swift] type-mappings with a dot doesn't work without modelNamePrefix

Bug Report Checklist

• 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?
• Have you searched for related issues/PRs?
• What's the actual output vs expected output?
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Description

I'm trying to use a reference to a shared external module with the type-mappings option. Unfortunately, dot character seems to be discarded except if modelNamePrefix is also defined.
It might be an expected behaviour, but I couldn't figure it out from the documentation, so I'm assuming this is rather an issue.

openapi-generator version

6.6.0

OpenAPI declaration file content or url

https://gist.github.com/jrmybrault/838da0557d6851bea3fb672e4384e342

Generation Details

WITH a modelNamePrefix

openapi-generator generate \
-g swift5 \
-i Contracts/get-user.yml \
-o ../Generated/GetUser/ \
-c openapi-generator-config.yml \
-t custom-templates \
--global-property models,apis,supportingFiles=false,apiDocs=false,modelDocs=false,apiTests=false,modelTests=false \
--additional-properties=projectName=GetUserAPI,modelNamePrefix=GetUserAPI \
--type-mappings=GetUserAPIIdentity=BackendServices.Identity

import BackendServices

public struct GetUserAPIUserInformation: Equatable, Codable {

    public let identity: BackendServices.Identity

    public init(identity: BackendServices.Identity) {
        self.identity = identity
    }
}

Now, WITHOUT a modelNamePrefix:

openapi-generator generate \
-g swift5 \
-i Contracts/get-user.yml \
-o ../Generated/GetUser/ \
-c openapi-generator-config.yml \
-t custom-templates \
--global-property models,apis,supportingFiles=false,apiDocs=false,modelDocs=false,apiTests=false,modelTests=false \
--additional-properties=projectName=GetUserAPI \
--type-mappings=Identity=BackendServices.Identity

import BackendServices

public struct UserInformation: Equatable, Codable {

    public let identity: BackendServicesIdentity

    public init(identity: BackendServicesIdentity) {
        self.identity = identity
    }
}

Notice the dot character has been discarded, thus making the compiler search for a BackendServicesIdentity type that doesn't exist, instead of looking for an Identity type within the BackendServices module.
Adding quotes or an escape character doesn't seem to make a difference.

Steps to reproduce

Just use commands mentioned above.

Related issues/PRs

Suggest a fix

Start by reproducing the two swift5 generation commands using Contracts/get-user.yml, openapi-generator-config.yml, and the custom-templates directory. Compare generated Swift output with and without modelNamePrefix, then trace the type-mappings handling. Done means a dotted mapping such as BackendServices.Identity remains qualified without modelNamePrefix.