Implement basic 301 Redirect for DSpace 6.x URLs when SSR is used.

[tdonohue]

References

• Fixes Return HTTP 301 to client when redirect occurs for old DSpace 6.x URLs #2265

Description

Minor changes to the dso-redirect.service.ts to ensure it returns a 301 Moved Permanently redirect when running during server side rendering (SSR). This required changes to the existing HardRedirectService to support 301 redirects.

Added specs for all changes as well.

Instructions for Reviewers

• Attempt to reproduce bug in Return HTTP 301 to client when redirect occurs for old DSpace 6.x URLs #2265 using /handle/[prefix]/[suffix] paths to an existing Community, Collection or Item.
• Verify that a 301 redirect now occurs.

[tdonohue]

@artlowel : Wondering if you or someone on your team could glance at this? I was looking into fixing this SEO issue after talking to Google Scholar today, and this is a "basic fix" (may not be perfect, but it works). Not sure whether to go down this path for 7.6, or just press pause and work on a better fix for a later release.

[artlowel]

Thanks @tdonohue!

This works. However I think the cleaner way to do it would be to use HardRedirectService for this. Its purpose is to handle redirects, and it already has separate implementations on the browser and server so you wouldn't need the platform check in DsoRedirectService

It would be slightly more complicated though, as we'd need the option to pass a 3xx status code as a param to HardRedirectService's redirect method (as currently it always redirects with a 302)

So if we still want to include this fix in 7.6 I'd use this PR. If it's not that urgent, perhaps wait for a PR based on HardRedirectService

[tdonohue]

@artlowel : I quickly refactored this to just use the HardRedirectService (adding an optional statusCode param). This is still working well for me. Could you give it a quick test / review tomorrow?

[artlowel]

Thanks @tdonohue!