The variable was documented as database_username, but should be database_user.

Change-Id: Ia1fd8f9a9336c26520041fa2138c763a8c382bca

Closes-Bug: #1804850
Change-Id: Icb7edbac5df316af68972cafa448a261c26747b0

Change index to ease identify what service want to look.
Split docs into more specific folder such as networking
and storage.

Change-Id: Ic7ac12b3dd555fa5c018eeb897ccd4a5a2dfe8f3