Prior to this commit, all forward outcomes resulted in a 404. This
commit changes request and data guards so that they are able to provide
a `Status` on `Forward` outcomes. The router uses this status, if the
final outcome is to forward, to identify the catcher to invoke.
The net effect is that guards can now customize the status code of a
forward and thus the error catcher invoked if the final outcome of a
request is to forward.
Resolves#1560.
This follows the completed graduation of stable contrib features into
core, removing 'rocket_contrib' in its entirety in favor of two new
crates. These crates are versioned independently of Rocket's core
libraries, allowing upgrades to dependencies without consideration for
versions in core libraries.
'rocket_dyn_templates' replaces the contrib 'templates' features. While
largely a 1-to-1 copy, it makes the following changes:
* the 'tera_templates' feature is now 'tera'
* the 'handlebars_templates' feature is now 'handlebars'
* fails to compile if neither 'tera' nor 'handlebars' is enabled
'rocket_sync_db_pools' replaces the contrib 'database' features. It
makes no changes to the replaced features except that the `database`
attribute is properly documented at the crate root.
The new examples directory...
* Contains a `README.md` explaining each example.
* Consolidates examples into more complete chunks.
* Is just better.
Resolves#1447.
