Add quick connect (login without typing password)

[ConfusedPolarBear]

Changes

This PR adds a new login method for devices that do not have a keyboard to enter a username/password on (smart TVs) or have limited keyboard input. It is a recreation of other quick sign in solutions found in other products (such as Plex, YouTube and Amazon Prime).

Proposed login flow:

• The server administrator enables quick connect (only done once)
• A user opens the Jellyfin app on a device they want to watch content on, selects the quick connect login option and is displayed a 6 digit code
• The user uses a device which is already authenticated to the Jellyfin server (such as their phone or computer) and enters the code displayed on the other device
• The server authorizes the connecting device to login as the user account that typed in the code

Proposed changes, feedback, and UX changes are welcome.
Related PR: Server side code

Planned features for this PR:

• Proof of concept
• Save quick connect state between server restarts
• Get new icons for quick connect links

Issues

Closes feature request 541.

[YouKnowBlom]

Aside from that this looks great! It'll be really convenient to have :)

[dkanada]

We are migrating to ES6, so if you want to update your files it would be excellent but not required. We are also fixing the casing of folders and files to use camelCase so please rename them to match that standard.

[ConfusedPolarBear]

I've renamed the files to use camelCase but I'm not fluent enough in JavaScript to migrate to ES6

[heyhippari]

I'm not fluent enough in JavaScript to migrate to ES6

No worries, that's not blocking. We'll take care of it ;)

[heyhippari]

Do note that due to #1007, you might have to submit your API client changes to https://github.com/jellyfin/jellyfin-apiclient-javascript instead of here, though.

[dkanada]

Apologies for all the merge conflicts, we have been going through some drastic changes from stricter linting rules and more CI additions.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
5.9% Duplication

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 1 Security Hotspot to review)
143 Code Smells

No Coverage information
4.3% Duplication

[thornbill]

These changes look great overall! Just a couple small pieces of feedback.

[sonarqubecloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
2.3% Duplication