Issue Summary

This is reproducible on Data Center: (no)

Steps to Reproduce

1. Create an import using the import from URL functionality
2. Provide a URL with already encoded values
   E.g https://url.com?token=11%3D22

Expected Results

The import source can be saved successfully and the data fetched from the URL

Actual Results

The URL is encoded again.
In the URL provided above: https://url.com?token=11%3D22 the `%3D` is the encoding for `=`
When we encode it again the URL becomes https://url.com?token=11%253D22
because the the encoder sees `%` as an invalid character and encodes it as `%25`

The below exception is thrown in the xxxxxxx.log file:

...

Workaround

Do not upload a URL with any encoded special characters
E.g make https://url.com?token=11%3D22 -> https://url.com?token=11=22 

Please see list of special characters: https://developer.mozilla.org/en-US/docs/Glossary/percent-encoding