Enhance error message on incorrect organisation/repo name

[kokerinks]

Summary:

Fixes #376

Type of change:

• ✨ Enhancement

Changes Made:

• Added a new error message repoOwnerNotPresentMessage, which will show now when the repo owner (i.e. organisation or username) in OWNER_NAME/REPO does not exist
  • originally showed the message repositoryNotPresentMessage instead

Screenshots:

In repo selection page:

After submitting:

Works for other repo-switching functions as well:

Proposed Commit Message:

Enhance error message on incorrect organisation/repo name

The original error message for incorrect repo name does not specify 
whether the mistake is in the org name or repo name.

Hence, let's add an additional error message to show if the 
organisation name could not be found. This will give users an easier 
time finding the error and rectifying it when keying in a repo.

Checklist:

• I have tested my changes thoroughly.
• I have created tests for any new code files created in this PR or provided a link to a issue/PR that addresses this.
• I have added or modified code comments to improve code readability where necessary.
• I have updated the project's documentation as necessary.

[nknguyenhc]

@kokerinks If your PR is ready for review, do mark it as ready so that we can start the review process.

[kokerinks]

@nknguyenhc marked as ready for review 👍

[nknguyenhc]

Nice job on following our coding convention!

nknguyenhc is a valid Github profile. You may want to check for whether the user exists as well, and change the error messages from "invalid organisation" to "invalid organisation/user"

[kokerinks]

@nknguyenhc I have made the required changes, feel free to review again

[nknguyenhc]

When a user is viewing a repo and changes to an invalid repo,

1. Expected behaviour: Error message pops up and user can continue viewing the previous valid repo. This is also the behaviour before this change.
2. Actual behaviour: Error message pops up, but the user cannot continue viewing the previous valid repo.

[kokerinks]

@nknguyenhc Have addressed issues again in latest commits, let me know if there's any other changes to be made!

[nknguyenhc]

LGTM!