Umar/5124 create external resource with add links

[umar8hassan]

What are the relevant tickets?

Closes https://github.com/mitodl/hq/issues/5124

Description (What does it do?)

This change is aimed to add External Resources on Link Add/Update. The syntax used for Link will be replaced with syntax for Resources in Markdown i.e. {{ % resource_link "uuid" "title" % }}

How can this be tested?

1. Switch to umar/5124-create-external-resource-with-add-links branch in ocw-studio
2. Open text editor
3. Add a link

4. The syntax of link should be replaced with resource syntax in editor 5. The resource should not be editable

6. Type a URL and upon space/enter, it should convert to a Resource Link

• If the same URL as above, verify that the existing resource ID is being used.
• If a different URL a new resource id will be used

7. verify the use case without selecting any text and adding a link with the AddLink button

Additional Testing

Enable/disable OCW_STUDIO_CUSTOM_LINKUI_ENABLE feature flag on PostHog to enable/disable the feature for users.
Setup PostHog with instruction in the Readme.

[ibrahimjaved12]

Looks good to me

[pdpinch]

Is this behind a (posthog) feature flag? I want to be able to control the roll-out of this feature, limiting it to certain users until it's been thoroughly tested.

[pdpinch]

Is this blocked by #2291 ?

[umar8hassan]

Is this blocked by #2291 ?

Yes. It was. But I can rebase on the branch and work on it now, since PostHog has been integrated with core functionality. Additional changes for PostHog integration will be done later in separate tickets.

[ibrahimjaved12]

👍🏻

[umar8hassan]

Holding this since adding a link without selection ends up with both of Link and ResourceLink syntax being inserted. Need to resolve this before merging.

[pdpinch]

When fixing #2279 (comment) be sure to add a test

Otherwise this should get merged Thursday 9/26