AT:

• the tenant id of a case instance is inherit form the case definition, by default
• I can override the default behavior (e.g. set a tenant id when the case definition has no tenant id) and set a tenant id (e.g. based on a given context: definition, variables etc.)
• the SPI is also used when an instance is started by a call activity or case task and the called process / case instance is not assigned a tenant id either by inheriting it from it's definition nor from the calling instance
• when a case instance is started using a call activity or case task, the case instance inherits the super case / execution instance's tenant id if the definition has no tenant id