fix: do not check the same url more than once

[peterprototypes]

This is a fix for #2298

Before:

After:

I've used the https://github.com/organicmaps/organicmaps.github.io/ repo for the before and after tests.

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[peterprototypes]

@Keats looks like me and @biodranik worked on the same thing. I think his solution is a bit easier to follow, as it avoids the complexity of a nested HashMap. The only difference in end result is that I changed the output to show the number of unique external links instead of the total number of links.

[biodranik]

Printing the real number of unique urls that are checked is a good idea.

In my approach failures are also printed for each page where the same link was used, so you can see how often the failed link is used, and on which pages. Is it the same for your implementation?

[peterprototypes]

Printing the real number of unique urls that are checked is a good idea.

In my approach failures are also printed for each page where the same link was used, so you can see how often the failed link is used, and on which pages. Is it the same for your implementation?

Yes, it's the same. I also clone the result from the first checked link to all messages.

[biodranik]

Learning Rust in this way is a lot of fun! I've also updated my PR #2305, @Keats WDYT?

[Keats]

I think #2305 approach is a bit neater

[peterprototypes]

I think #2305 approach is a bit neater

Agreed 👍