feat: validate official marketplace source objects (#40)

* feat: validate official marketplace source objects

* test(scanner): update marketplace fixture for official source shape

* test(scanner): cover official marketplace source validation

* fix: harden marketplace validation

Signed-off-by: Michael Kantor <6068672+kantorcodes@users.noreply.github.com>

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Signed-off-by: Michael Kantor <6068672+kantorcodes@users.noreply.github.com>

Author: kantorcodes