Companion App 1.0.0 doesn't work with Self Signed SSL Certificate

Issue Summary

Companion App 1.0.0 doesn't work with Self Signed SSL Certificate

When Confluence is served behind a Self-Signed SSL Certificate, editing an attachment will not work and there isn't any error message logged in the companion.log either.

Tested Environment

Confluence 7.3.1
Confluence 7.4.0(EAP)
Companion App 1.0.0
Windows 10
MacOS

Steps to Reproduce

1. Install a fresh installation of Confluence
2. Setup Confluence to be serving on HTTPS using a self-signed certificate following this documentation
3. Configure the browsing computer to trust the self-signed SSL certificate following the Workaround in this KB
4. Confirm the browsing computer has Companion App v1.0.0 installed and it is running
5. Attach an attachment in Confluence Page
6. Edit the attachment using Companion App

Expected Results

Companion App should work as expected, allowing the user to edit the attachment locally

Actual Results

1. The browser pop-up requesting to launch Companion App is shown
   
2. Companion would ask for trusting the domain if it is the first time accessing to the Confluence
3. Browser's connection to Companion App timed out and display the message dialog for Companion App download
   
4. There isn't any error message logged in the companion.log
   Example log recorded in companion.log

   info:	adc:file-manifest 2020-04-06T01:20:13.874Z Launching custom protocol for Window. With args:["C:\\Users\\Damien\\AppData\\Local\\atlassian-desktop-companion\\app-1.0.0\\Atlassian Companion.exe","--allow-file-access-from-files","--original-process-start-time=13230609612993731","atlassian-companion:%7B%22link%22:%22https://localhost:2740/rest/token-auth/api/previews/templinksresource/companion/attachment?attachmentId=2064386&jwt=eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJzdWIiOiJqd3Quc3ViamVjdC5jb25mbHVlbmNlLXByZXZpZXdzLnRlbXBsaW5rc3Jlc291cmNlIiwicXNoIjoiMGVkZmEzMDg1NzVlYzY3MzI4ZjFkYzQxZGE4NjJiZTg4ZmE2ZjZmNjIxNzE4OGFhMjYxNWNmZTJiYWQ2N2UxNiIsImlzcyI6ImNvbS5hdGxhc3NpYW4uY29uZmx1ZW5jZS5wbHVnaW5zLnByZXZpZXdzIiwiZXhwIjoxNTg2MTM3ODExLCJpYXQiOjE1ODYxMzYwMTEsInVzZXJLZXkiOiIyYzk2ZGE3YzcxM2U3ZTA2MDE3MTNlODAxMTg3MDAwMCIsImp0aSI6ImJlZDI2ZmUxLWUxMDgtNDRmYS04OGYxLWVkMGJkNzU0YzU0MCJ9.1Gre2Y1jzO2n4c8XI9PwpSCpPtW36VySSNcFUVZRKk0%22%7D"]
   info:	adc:serverauth 2020-04-06T01:20:13.878Z Found trusted domain in database: localhost
   

Workaround

• Use CA-signed SSL Certificate or serve Confluence under HTTP in order to continue using the Companion App.