RPM Support

In libmodulemd, it is planned to introduce an extension to version 2 of modulemd documents which differ slightly from the current v2. A new, optional field is added, called "static_context", described thusly:

    # context:
    # Module context flag
    # The context flag serves to distinguish module builds with the
    # same name, stream and version and plays an important role in
    # automatic module stream name expansion.
    #
    # If 'static_context' is unset or equal to FALSE:
    #   Filled in by the buildsystem.  A short hash of the module's name,
    #   stream, version and its expanded runtime dependencies. The exact
    #   mechanism for generating the hash is unspecified.
    #
    #   Type: AUTOMATIC
    #
    #   Mandatory for module metadata in a yum/dnf repository.
    #
    # If 'static_context' is set to True:
    #   The context flag is a string of up to thirteen [a-zA-Z0-9_] characters
    #   representing a build and runtime configuration for this stream. This
    #   string is arbitrary but must be unique in this module stream.
    #
    #   Type: MANDATORY
    static_context: false
    context: c0ffee43

Source: https://github.com/fedora-modularity/libmodulemd/commit/2000e88d48a7b8d9fba1f7866d3709035dd2b957#diff-f693f5c1bd57e7782999ed7d59a4e2cdb1548c6d5e2e4663265f2165a949effeR81-R96

(see that commit also for document examples, and the names of libmodulmd functions)

See also: https://github.com/fedora-modularity/libmodulemd/commit/0132015b5729b6077d49fc5beb2c662a563c6e6d#diff-f693f5c1bd57e7782999ed7d59a4e2cdb1548c6d5e2e4663265f2165a949effe

Basic support is added in a previous issue (linked).

For full support, we need to analyze the impacts of this new flag on dependency solving, and ensure that we do the correct thing, and potentially implement the new behavior