generated search URL double encodes comma in collection id list

[rahulbot]

If I search against two collections, 34412234 and 262985232, I see this in the URL:

https://search.mediacloud.org/search?q=*&nq=&start=08-28-2025&end=09-30-2025&p=onlinenews-mediacloud&ss=&cs=34412234%252C262985232&any=any&name=*&edit=false

I expect the collections to be encoded as numbers with a comma between, which would be 34412234%2C262985232. However, what I see is 34412234%252C262985232. Note the use of %252C instead of %2C. %25 is "%", so I think this is being double encoded.

Fixing this needs to be done carefully, because it needs to support things people have bookmarked but also be fixed. Perhaps it could switch to support either cc (new proper format) OR cs (backwards compatible) as one way to make this fix cleanly?

[philbudne]

Looking in the requests.log file, it looks like %252C can appear in other contexts: Referer: https://search.mediacloud.org/search?q=mexico%252Ccartel&nq=&start=08-29-2025&end=10-01-2025&p=onlinenews-mediacloud&ss=&cs=34412427&any=all&name=mexico%20AND%20cartel&edit=false shows the pattern in the query string.