Basic `/internal/pages` endpoint that will be used for Pages virtual
domains internal API. The endpoint is currently behind feature flag and
provides authetication similar to how Workhorse is authenticating with
the GitLab.

The old rules meant that any future changes to these directories would
require the use of `git add -f` to be staged. This is problematic for
the upcoming FOSS-only mirror of GitLab. Any changes to be synced to
this mirror are staged using `git add --all .`, which due to the Git
ignore rules would not add the tmp/ and shared/ directories. This then
leads to various specs failing because they expect certain
sub-directories of these directories to be available.

This commit changes the rules so that we include the .gitkeep files,
ignore other files, and completely ignore anything in tmp/test. This
requires that the rules are specified in tmp/.gitignore and
shared/.gitignore, instead of the top-level .gitignore, without this I
could not get Git to include the .gitkeep files properly.

- Add mail interceptor the signs outgoing email with SMIME
- Add lib and helpers to work with SMIME data
- New configuration params for setting up SMIME key and cert files

This commit ignores the temporary cache directories that I _think_ are
created by the VSCode Ruby extension.

(cherry picked from commit 1b33828811897b6a3f8a38044cc0839b87098d1f)

This allows us (and others) to test drive Puma without it affecting all
users. Puma can be enabled by setting the environment variable
"EXPERIMENTAL_PUMA" to a non empty value.

For Geo, a file is created for configuration of the database. This file
shouldn't appear in CE, but if you've setup your GDK with a remote
pointing to CE and one to EE, this file might be around when switching
branches.

This will mark the workspace dirty, which annoys me more than it should.

[ci skip]

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

[ci skip]

[ci skip]