[FEATURE] read shared dataExtensions without parent access

[JoernBerkefeld]

issue: on some instances it is not allowed to get access to the parent BU.

topics to cover:

• [FEATURE] support project init (and BU refresh) from non-parent BUs #1186
• read shared dataExtensions without parent access (covered here)
• [FEATURE] read shared folders without parent access #1188