Setup of a Signal messenger server with corresponding Apps (iOS, Android) and use of API

We are looking for an expert with proofed experience on building and installing the Signal server sources by Open Whisper Systems on an Ubuntu Linux system and integrate that server with both Android and IOS platforms of the signal app.

Name of the application and icon of the apps need to be changed. The Apps must be available in Google play and Apple app store as hidden apps not public.
A code using the Signal API for the creation of a new key pair, identification of the recipient and sending/receiving a message with PDF attachments needs to be created.

A detailed documentation for each step of the installation process of the server including the modified files and lines of the original open whisper system code is required. This as well for both android and iOS app and the sample code for the use of the API.

Everything must be able updatable by us if there's a new update on the market for the signal application or server code. We need a detailed documentation of how to update the apps itself and the server.

Please see the attached order description for more details.

A work contract needs to be signed with respect to code ownership. Please see attached work contract.