Fix SWHID resolving when origin qualifier has an equal character in its value

I have stumbled upon this permalink which I get when I click copy permalink:

https://archive.softwareheritage.org/swh:1:dir:53ddae53e380c56cf74dd9ad06be87e1f83fa450;origin=https://cran.r-project.org/package%3DActivePathways;visit=swh:1:snp:9b706ec3d79576d295fca2980c546d6b760ffc54;anchor=swh:1:rev:191039b4497ec53153e480cacfa1df9b46b38e6e;path=/ActivePathways//

It yields a 404 error when used.

This does not happen with copy identifier:

swh:1:dir:53ddae53e380c56cf74dd9ad06be87e1f83fa450;origin=https://cran.r-project.org/package%3DActivePathways;visit=swh:1:snp:9b706ec3d79576d295fca2980c546d6b760ffc54;anchor=swh:1:rev:191039b4497ec53153e480cacfa1df9b46b38e6e;path=/ActivePathways/

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Migrated from T2641 (view on Phabricator)