A fixed name is too rigid, let's give users the ability to define
custom drop-in names which at the same time also allows defining
multiple dropins per unit.
We use ~ as the separator because:
- ':' is not allowed in credential names
- '=' is used to separate credential from value in mkosi's --credential
argument.
- '-' is commonly used in filenames
- '@' already has meaning as the unit template specifier which might be
confusing when adding dropins for template units
Daan De Meyer
82c2214539