Smart Linking: Prevent insertion of duplicate links

[acicovic]

Is your feature request related to a problem?

Our API back-end is markup/link agnostic. As such, when we use the Smart Linking feature multiple times on a post or Block, it is possible that a given URL could be inserted multiple times. In my own testing, I was able to insert the same URL 3 times in a paragraph block.

Describe the solution you'd like

We probably don't want this to be happening, especially in the same block. And we probably shouldn't have the same link in a post more than 2 times. When we get the results from the API, we could check if the given URL is already present in the post or block, and not include it in the results if this is the case.