I am currently developing a web-frontend which uses the REST API (via vuex-rest-api) 

Currently the ETag Header is only sent when i GET a ressource.

Now, when the user changes parts of the ressource and i update it using a PUT 
request (encapsulated in a POST) i get back the changed parts, but no ETag Header.

The same happens when the user creates a new ressource with a POST request i 
get back the id and URL, but also no ETag Header.

Therefore i always need to issue an additional GET request on the same ressource 
afterwards to have the ETag information for further editing (PUT'ing) the ressource.

Which is 1) ressource consuming and 2) not convenient ;)

So the Question is: 

is the current behaviour by design ? 

or can we change it so that the Etag Header gets sent automatically when issuing PUT, POST or PATCH.

regards,
marcus.