chore: Add SPDX headers and REUSE CI workflow

[susnux]

* ⚠️ this is chained on #5647

☑️ Resolves

Add SPDX headers to all files

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 3️⃣ Backport to next requested with a Vue 3 upgrade

[AndyScherzinger]

@susnux many files lack the year for the copyright text line. The simplest is to add the year of the first commit for each file.

[AndyScherzinger]

The year isn't mandatory but strongly suggested I would say.

[AndyScherzinger]

Fine by me to merge, still some files missing the year info, which is fine I guess, any header is better than none 👍

[AndyScherzinger]

@ShGKme fine to merge? Changes needed? :)

[AndyScherzinger]

/backport to next

[ShGKme]

There are still globs in reuse with glob extension (see comment above). I was told by @nickvergessen that this is not good as may potentially take more files than needed.

Other than that looks fine. Checked with https://github.com/nextcloud/github_helper/tree/master/spdx-convertor adjusted to this repo.

[AndyScherzinger]

@ShGKme you mean #5650 (comment) as in the wildcards are to wide?

[AndyScherzinger]

@susnux I'll take care of fixing the images and licenses in reuse 👍

[ShGKme]

@ShGKme you mean #5650 (comment) as in the wildcards are to wide?

Yes, but I haven't found Joas's comment about it in Talk Desktop's PR, may be It was in my dream.

confirming with Joas

[ShGKme]

No, this is not correct with this glob, same as it was on server.
Some files are not from Nextcloud, see:
https://github.com/nextcloud/server/blob/59c181b4cbc47821d0a7d35df747a8b1d012dfc7/.reuse/dep5#L158-L160

We should copy this block from server (and somehow maintain it 🥲)

[AndyScherzinger]

No, this is not correct with this glob, same as it was on server.

Ah, yes. That I will fix myself on this PR since I also did that on server including replacing the icon for Material Symbol ones 👍

Thanks for the feedback @ShGKme - now it is clear to me what needs to be done 👍

[AndyScherzinger]

@ShGKme see b56a8b5 for replaced icons and license info 👍

[backportbot]

The backport to next failed. Please do this backport manually.

# Switch to the target branch and update it
git checkout next
git pull origin next

# Create the new backport branch
git checkout -b backport/5650/next

# Cherry pick the change from the commit sha1 of the change against the default branch
# This might cause conflicts, resolve them
git cherry-pick 73ea7253 d451d1bd f33d8db9 b56a8b5b

# Push the cherry pick commit to the remote repository and open a pull request
git push origin backport/5650/next

Error: No changes found in backport branch

---

Learn more about backports at https://docs.nextcloud.com/server/stable/go.php?to=developer-backports.

[AndyScherzinger]

@susnux could you maybe take care of the forward porting to next? No hurries/rush

[susnux]

@AndyScherzinger yes