Make LOCK operation a separate object verb

Is your feature request related to a problem? Please describe.

I'm always frustrated when I can't restrict how LOCK operation is available or not to users. Currently it's a PUT of LOCK object wrt ACL restrictions.

Describe the solution you'd like

Add a LOCK verb. It's pretty straightforward for EACL and tokens, however there is a problem of basic ACL. It can be solved in different ways:

• treat it the same as PUT there
• repurpose one of the (mostly) useless verbs like GETRANGEHASH (can be combined with reserved bit flip, we've got two spare there)
• extend basic ACL with one more integer
• extend basic ACL type to uint64 (in a different protobuf field of course)
• use an attribute for additional basic ACL integer
• move basic ACL to attributes altogether

Each has its pros and cons.

Describe alternatives you've considered

We need LOCK itself, the operation is radically different from PUT and it can be useful to not mix them (allow to PUT and forbid LOCK or allow LOCK and forbid PUT).

Start by reviewing the API and proto definitions for the current LOCK-as-PUT behavior, including EACL, token, and basic ACL handling. The work is done when LOCK is represented as a separate verb and its basic ACL representation is selected and documented consistently with the proposed alternatives.