Rewrite server side copy and 'object post as copy' feature as middleware to
simplify the PUT method in the object controller code. COPY is no longer
a verb implemented as public method in Proxy application.
The server side copy middleware is inserted to the left of dlo, slo and
versioned_writes middlewares in the proxy server pipeline. As a result,
dlo and slo copy_hooks are no longer required. SLO manifests are now
validated when copied so when copying a manifest to another account the
referenced segments must be readable in that account for the manifest
copy to succeed (previously this validation was not made, meaning the
manifest was copied but could be unusable if the segments were not
readable).
With this change, there should be no change in functionality or existing
behavior. This is asserted with (almost) no changes required to existing
functional tests.
Some notes (for operators):
* Middleware required to be auto-inserted before slo and dlo and
 versioned_writes
* Turning off server side copy is not configurable.
* object_post_as_copy is no longer a configurable option of proxy server
 but of this middleware. However, for smooth upgrade, config option set
 in proxy server app is also read.
DocImpact: Introducing server side copy as middleware
Co-Authored-By: Alistair Coles <alistair.coles@hpe.com>
Co-Authored-By: Thiago da Silva <thiago@redhat.com>
Change-Id: Ic96a92e938589a2f6add35a40741fd062f1c29eb
Signed-off-by: Prashanth Pai <ppai@redhat.com>
Signed-off-by: Thiago da Silva <thiago@redhat.com>