Fix flux install command so it returns an error when unexpected arguments are passed

[VinGarcia]

This PR was implemented to address the issue reported by myself on #4403.

I made sure that it is working on the cases where there are only flag arguments, or no arguments.

I wanted to add a test for a successful run, but when I tried I actually got an "install failed" error. So I figured that maybe there was a reason why no successful tests were present.

I can add more tests, but I would need some guidance.

[makkes]

There's a much simpler solution here by using the Args field of Command:

var installCmd = &cobra.Command{
	Args: cobra.NoArgs,

[VinGarcia]

@makkes just implemented your suggestion, thanks =]

[stefanprodan]

@VinGarcia can you please squash all commits into one and rebase.

[VinGarcia]

@stefanprodan and @makkes just squashed the commits, it should be ready now.

[makkes]

One thing that bothers me a little here is that this PR only fixes this for the install command but all the others stay the same. Running flux check foobar still succeeds while flux install foobar fails. I personally would like to strive for consistency here. @stefanprodan wdyt?

[VinGarcia]

@makkes I could add these changes on either this PR on a separate one. I would just need the list of commands on which to do it.

[VinGarcia]

@makkes and @stefanprodan how should we proceed?

[stefanprodan]

Rebase with the main branch and force push please.

[makkes]

Let's add a proper Args setting to each command.

[VinGarcia]

@makkes I started going over all instances of cobra.Command and checking flux [command] --help for each of them, the ones with no args I will add Args: cobra.NoArgs, but some of them like cmd/flux/bootstrap_bitbucket_server.go do not have unit tests, so I have three options:

1. Not add unit tests at all
2. Only add tests to the files that already have unit tests
3. Write unit tests for all files even the ones that don't have _test.go files already.

The last option might be hard for me, and I don't know how much important you guys think 2. is.

[stefanprodan]

I don't think we need to test a builtin feature of cobra on each command. We can take this in for install. @VinGarcia if you feel up to it, please do bootstrap and others commands in a followup PR. To get this merged you have to rebase with upstream main branch and force push, this PR should contain a single commit.

[makkes]

There is a certain chance that adding the wrong PositionalArgs to a command would result in the command not being usable, anymore, e.g. when adding cobra.NoArgs to the get ks command. I suggest it is desirable writing a unit test that verifies this doesn't happen.

I agree with Stefan that adding PositionalArgs to each command should be made in a subsequent PR and we keep this one focussed on what's said in the title.

[VinGarcia]

@makkes and @stefanprodan its rebased/squased into a single commit, I will continue the work on a separate PR then.

Thanks

[makkes]

Thanks @VinGarcia! 🤜🏻🤛🏻