This commit changes request method for "categories/search" from GET to
POST to make sure that long filters can be passed to the server. For
example, category selectors with many categories are setting the full
list of selected category IDs to ensure these are filtered out from the
list of choices. This can result in a long URL that exceeds the maximum
length.
- Run the CSP-nonce-related middlewares on the generated response
- Fix the readonly mode checking to avoid empty strings being passed (the `check_readonly_mode` before_action will not execute in the case of these re-dispatched exceptions)
- Move the BlockRequestsMiddleware cookie-setting to the middleware, so that it is included even for unusual HTML responses like these exceptions
