How do I connect customers using APIs?

[Carlos A_ López Ortín]

Hello, experts:

Sorry if this looks similar to my last question, but I'm lost and have no clue where to go. So let's start from the beginning, shall I?

Well, I'm developing a customer portal, and I need to integrate Jira issues on it. My customers must see their issues, comments and worklogs, and also, being capable of write new comments and maybe new issues.

Now, our company is using an "Atlassian portal", where users logs in and retireve that information. I don't know if it's a helpdesk application, if it's using Jira or a Service Desk. I'm not administrator, so it's all I can tell.

So, our customers have an account, but they don't have Jira or any Atlassian app installed. They don't have any kind of permissions or access to our company data. Just the portal.

I need to implement the app to connect to Atlassian via API, using oAuth2, with our .NET Core app. By this time, using this guide:
https://developer.atlassian.com/cloud/jira/service-desk/oauth-2-authorization-code-grants-3lo-for-apps/
I was able to connect to Kira API, using my account, and get all the info, but if I try using a different account it tells me that I have no permission.

Ok, I got it, it was because the app was registered in my developer.attalsian.com account, and it's not a shared one, but if I create a "new app" on the different account, change the connection params, and try again (making the new account the "owner" of the app), it says that "You don't have an Atlassian Jira site to connect 'YourAPP' to".

I tried to change scope options from "read:jira-work%20read:jira-user" to "read:servicedesk-request" in order to try to connect to service-desk, but it tells me that Service Desk is not installed either.

So, I don't know how to connect that customer to our data. I don't know if I have to connect to Jira API, Service Desk-API or what. Also, I read about user impertionation connection:
https://developer.atlassian.com/cloud/jira/service-desk/user-impersonation-for-connect-apps/
But I don't understand the process: the first step says "Admin installs the app: This initiates the installation handshake with the oauthClientId and the shared secret in the request body". Do I really have to install something? What or where is that addon-key and oauthClientId? Should I ask to Jira or send to "https://auth.atlassian.com/oauth/token"?

I don't know. We need that users can login on our APP, go to "support" tab and start reading issues and posting comments, and if they don't need to log in Jira or whatever, the better.

Thank you. Sorry for the long post, but I tried to be as clear as possible, because I was reading documentation for a week, and triying for two days with no luck.