We have been discussing about this merge for a while.
Its main goal is to simplify things: code navigation, but also
packaging.

The rationale is that the code is more cohesive in this way, and there's
only one source package to install.

Dependencies that are only for the server or the client will not be
installed by default, and they are expected to be provided by the
environment. There are setuptools extras defined for the client and the
server.

Debianization is still expected to split the single source package into
3 binaries.

Another avantage is that the documentation can now install a single
package with a single step, and therefore include the docstrings into
the generated docs.

- Resolves: #8896

- Resolves: #8804

- rename add_tag method
- reorder blob interface methods for clarity
- use mkdir_p from leap.common

Add a DELETE method for blobs server and integrate it into client's
BlobManager.
- Resolves: #8846

Check if user and blob_id are valid strings, then check if the resulting
path is a subdirectory of blobs configured path.

- Related: #8800

_validate will check if user_id and blob_id are letter, numbers, dashes
and underscores. It is called on render_GET and render_POST, validating
incoming arguments before handling on backend.

- Resolves: #8832