Fix #3804, Fix #5776

To support Exoscale

Change the behaviour of remotable concern. Previously, it would skip
downloading an attachment if the stored remote URL is identical to
the new one. Now it would not be skipped if the attachment is not
actually currently stored by Paperclip.

The default limit of 10 retries with exponential backoff meant
that if the S3 server was timing out, you would be stuck with it
for much, much longer than the 5 second read timeout we expect.

The uploading happens within a database transaction, which means
a failing S3 server could negatively affect database performance

I also added "public" here, as I can't think of a good reason not to add it. Perhaps it has some marginal benefit in that ISPs (or other proxies) can cache it for all users. The assets are certainly publicly available and the same for all users.

Still check for S3_CLOUDFRONT_HOST for existing installs.

* Fix uncaching worker

* Revert to using Paperclip's filesystem backend instead of fog-local

fog-local has lots of concurrency issues, causing failure to delete files,
dangling file records, and spurious errors UncacheMediaWorker

* Update paperclip.rb

* Update .env.production.sample

* Update paperclip.rb

This reverts commit 40871caa4b.

* Revert "Bump version to 2.3.2rc1"

This reverts commit cdf8b92fea.

* Revert "Downgrade Dockerfile to Ruby 2.4.3 on Alpine 3.6 (#6806)"

This reverts commit 0074cad44f.

* Revert "Handle Mastodon::HostValidationError when pulling remoteable assets (#6782)"

This reverts commit 4a0a19fe54.

* Revert "Correct the reference to user's password in mastodon:add_user task (#6800)"

This reverts commit 338bff8b93.

* Revert "Upgrade Paperclip to version 6.0.0 (#6754)"

This reverts commit b88fcd53f7.

Keystone V2 is deprecated in favour of V3. This adds the necessary
connection parameters for establishing a V3 connection. Connections
to V2 endpoints are still possible and the configuration should
remain compatible.

This also introduces a SWIFT_REGION variable for multi-region
OpenStack environments and a SWIFT_CACHE_TTL that controls how long
tokens and other meta-data is cached for. Caching tokens avoids
rate-limiting errors that would result in media uploads becoming
unavailable during high load or when using tasks like
media:remove_remote. fog-openstack only supports token caching for
V3 endpoints, so a recommendation for using V3 was added.

* Fix #1642, fix #1912 - Previous change (#1718) did not modify how original file was saved on upload

* Fix for when file is missing

* Custom Paperclip path.

* Document PAPERCLIP_ROOT.

* Add PAPERCLIP_ROOT_URL (and rename PAPERCLIP_ROOT to PAPERCLIP_ROOT_PATH).

add support for reading S3 protocol from ENV
also add S3_HOSTNAME in .env.production.sample

If an :original gets converted into another format, it would get saved as
original_filename *anyway*, so generating the extension is pointless and
yields bad results for when you change the style definition later. This way,
old gifs will still have correct URLs

for avatars/headers, resize avatars down to 120x120 instead of 300x300. Set cache headers on S3 stuff, also
make it private (aka only accessible via expiring links to prevent hotlinking)