Add option `--qos` (QoS revisited)

[onnozweers]

We (ab)used QoS (quality of service) for staging 5 years ago, because we had no bulk service yet. Now, staging works with the bulk service.

QoS may still be interesting to users. So, we may consider adding options to Ada to work with QoS. I'm thinking of:

# Setting QoS policy for a file or directory
ada --qos /directory/[file] [tape|disk+tape|disk|...]

# Listing available / configured QoS policies
ada --lsqos

[onnozweers]

Was reading https://github.com/dCache/dcache/blob/master/docs/TheBook/src/main/markdown/cookbook-qos-policies.md

It seems there is a separate option to set the QoS Policy for a file. As I understand it:

• A QoS is a fixed property and can be set to disk, disk+tape or tape. dCache may support new QoS'ses in the future.
• A QoS policy is admin defined and can have several stages or phases over time. In a QoS policy, you can also define how many replicas you want of a file. Since only admins can create a new QoS policy, I'm not sure whether we need Ada to handle this. Assigning a policy to a file or dir though is a user operation and should be implemented in Ada.

To reflect this, Ada should have separate options for this:

ada --qos <path> [disk|tape|disk+tape|...]
ada --qospolicy <path> <policy>

It would be nice to define QoS policies to allow users to create multiple replicas of files (for "hot" data).

Examples of how to define QoS policies in JSON are in the cookbook-qos-policies linked above.