Use the router-stripped route_path when building request-derived export
URLs, so table, row, and query JSON/CSV links do not apply base_url twice.
Keep urls.path() behavior unchanged, and add coverage for both /prefix/
exports and a /data/ base_url with a data database.
Closes#2759
* Dash encoding functions, tests and docs, refs #1439
* dash encoding is now like percent encoding but with dashes
* Use dash-encoding for row PKs and ?_next=, refs #1439
* Use dash encoding for table names, refs #1439
* Use dash encoding for database names, too, refs #1439
See also https://simonwillison.net/2022/Mar/5/dash-encoding/