[FEATURE]: Enable HEAD on nested entities

[MartinPankraz]

Is your feature request related to a problem? Please describe.
SAP Cloud SDK requests CSRF token for nested entities using HEAD

Describe the solution you'd like
Have the HEAD operation available for all entities or get rid of the oeprations for the API completely

Describe alternatives you've considered
Individual implementations can use the root '/' to perform the HEAD for the CSRF token, but SAP's Cloud SDK does not.

Additional context
In line with the work done for OData here