Start scheduler fails with arguments "-s PushStaged"

[r4ntix]

Describe the bug
According to the prompt of the command line, I tried to start the service with the -s parameter:

./target/debug/ballista-scheduler --help
Usage: ./target/debug/ballista-scheduler [ARGUMENTS...]

Arguments:
        -s, --scheduler-policy    The scheduing policy for the scheduler, see
                                  TaskSchedulingPolicy::variants() for options.
                                  Default: PushStaged

the result was an error:

./target/debug/ballista-scheduler -s PushStaged
Error: Failed to parse argument '--scheduler-policy': Invalid variant: PushStaged.

Hint: the value must be The scheduler policy for the scheduler.

Describe the solution you'd like
In this code:

// an enum used to configure the scheduler policy
// needs to be visible to code generated by configure_me
#[derive(Clone, ArgEnum, Copy, Debug, serde::Deserialize)]
pub enum TaskSchedulingPolicy {
    PullStaged,
    PushStaged,
}

clap ArgEnum derive macro generate possible values pull-staged, push-staged, not PullStaged, PushStaged

There are two solutions:

1. Modify the help doc to make it clear that the -s parameter values are pull-staged, push-staged.
2. Modify the TaskSchedulingPolicy enum and add #[clap(rename_all = "camel")], it generate possible values pullStaged, pushStaged

I can submit a PR for this, but need some suggestions.

[avantgardnerio]

I'm for solution # 1. There is a multi-decade tradition of this being "the unix way".

[r4ntix]

@avantgardnerio I have submitted a PR for this :)

[yahoNanJing]

Thanks @r4ntix for the refinement.