fix: do not partial match url params extraction

[Lazyuki]

Description:

Fix for #16137.

Custom Action Dimensions have an option to automatically extract values from the URL Search Parameters. As mentioned in the docs, it does not allow using Regex because it's supposed to be a "simple" match. One would assume it's doing a simple check to fetch the exact match for the URL parameter.
However, it's actually constructing a partial match with the regex \?.*pattern=([^&]*). This works fine in most cases, but if the pattern is included in another pattern's word ending, this regex picks that up instead.

So imagine trying to extract the type parameter from the URL

https://example.com/search?type=foo&date=bar&contenttype=baz

It should match type=foo and returns foo in theory, but current regex actually matches type=baz at the end from contenttype=baz because the regex is only searching for a parameter that ends with the specified pattern, in this case type. To fix this, we know that valid URLs don't have ? or & unless they are for search params (as they should be URL encoded otherwise), we can construct the regex [?&]pattern=([^&]*) instead to make sure the exact pattern is matched in the URL.

Review

• Functional review done
• Potential edge cases thought about (behavior of the code with strange input, with strange internal state or possible interactions with other Matomo subsystems)
• Usability review done (is anything maybe unclear or think about anything that would cause people to reach out to support)
• Security review done
• Wording review done
• Code review done
• Tests were added if useful/possible
• Reviewed for breaking changes
• Developer changelog updated if needed
• Documentation added if needed
• Existing documentation updated if needed

[github-actions]

This issue is in "needs review" but there has been no activity for 7 days. ping @matomo-org/core-reviewers