[Vue Rewrite] Add Feed Component

[devlinjunker]

Related to #748

Follows #2305
(Hopefully the file diff will be updated to only show the new files after this is merged... otherwise view 582b287...ab22ed4 for diff - or I can create a new PR after that #2305 is merged)

🗒️ Summary

Add Component for Adding New Feeds to the Database

• Add Feed URL to submit to backend endpoint (for adding feed to DB)
• Checks if Feed URL exists in Feedlist managed by Vuex Store
• Allows adding to Folder
• Allows creating new Folder and adding to that
• Checks that New Folder Name does not exist
• Allows entering username/password that can be used to access feed
• Provides control for sending autoDiscover parameter to backend endpoint
• Uses Vuex to update list of Feeds available on response from backend

✅ Checklist

• Code is properly formatted
• Sign-off message is added to all commits
  - [ ] Changelog entry added for all important changes. (Can we add the label to prevent the check for changelog? oh seems like the check was removed 🤔 so I'll just cross these out for most of these component PRs.. )

📷 Visual

add feed:

add feed to existing folder:

add feed and create folder:

add with credentials:

attempt add again:

create existing folder:

➡️ Up Next

• Look into Three Panel Layout for displaying Feeds + Items (Bookmarks App seems like Good Example...)
• Move API Requests to Service Classes (to be shared between stores and prevent stuff like having to duplicate api requests like here…)
• Sidebar Actions

[Grotax]

I think if this branch is rebased on the vue-rewrite branch it should only include the changes of the actual PR.

Thanks for your work I really appreciate it that you take the time an effort to go though this major mess :)

[devlinjunker]

Looks like rebasing did the trick and the files tab now only shows the changes for getting the Add Feed Component to work,

I think this should be ready to merge also once the builds pass, I've started on displaying the starred items and will be getting a PR out for that in the next couple of days once I get the layout working

and no problem about helping out! It's a great opportunity to learn Vue, and it's pretty easy for me to focus on creating a frontend for an already functional backend rather than having to do both at the same time (I've also loved using RSS for a while and if I understand how the frontend works here I can try to add more features I've been pining for once we have a functioning application that is up to the more recent standards)

[devlinjunker]

oh, seems like the changelog enforcer job ran on this... can we add the label? and I think this is ready to merge if no one else plans on reviewing it