Fix/signed wire threshold export 2004

Closes front#2004 (closed)

Summary

Users could not view their own and others paywalled content. See the steps on the issue above and try it out for yourself.

Test

1. Make a paywalled media post (image)
2. Refresh and check you can click the unlock button and see the image
3. Go to the media page for the image
4. Check you can see the image (note the url)
5. Log out
6. Visit URL - should not be able to access
7. Visit the channel that posted the paywalled image, try unlock the post. You should be prompted to send tokens.

Possible areas of regression

To test, I think we should test a variety of different media types, some with paywall and some without, from multiple accounts, and logged out, to ensure that everything is working.