Use the same parameter names for tag_key and key in ITEM_TAG endpoints

Specifications ITS
1

In Get EHR tags, the query parameters are all prefixed with tag_ (e.g., tag_key).

In Delete COMPOSITION tags and Delete EHR_STATUS tags, the parameters are not prefixed (e.g., key).

I propose that both key parameters are renamed to tag_key.

I also propose to rename the Get EHR tags to “Get Item tags” since the tags don’t belong to EHR but to COMPOSITION and EHR_STATUS.