using `instance-type` contraints parameter with string containing spaces character

[dave]

When trying to bootstrap a new controller using `instance-type` parameter where the possible values would contain space characters like "4GB Standard Instance" that is not possible, as juju client would consider each part as individual parameters.
Trying different method to escape the spaces don't help either.

example:
```juju bootstrap rackspace/lon ctrl --bootstrap-constraints 'instance-type=4GB Standard Instance'```

would output
```ERROR malformed constraint "Standard"```

Regards,
Dave

[Ian Booth (wallyworld)]

There's this PR recently added to allow zone constraints with spaces.

https://github.com/juju/juju/pull/11500

It seems there needs to be a similar fix across other constraint attributes.

[Achilleas Anagnostopoulos (achilleasa)]

@Ian: I have a quick fix for this which basically allows you to escape spaces anywhere inside a constraint string via a slash just as you would do in a shell, e.g:

--constraints arch=amd64 instance-type=with\ spaces zones=az\ one,az2

But it looks like the PR you just linked (hasn't landed yet though) adds space support for all constraint KV pairs without the need to manually escape spaces so I guess we can go with that one instead since it looks like it has already been reviewed.

Also linking the relevant bug for zones: https://bugs.launchpad.net/juju/+bug/1847259

[Achilleas Anagnostopoulos (achilleasa)]

PR https://github.com/juju/juju/pull/11500 which fixes https://bugs.launchpad.net/juju/+bug/1847259 also fixes this one as well.

[Achilleas Anagnostopoulos (achilleasa)]

My previous comment was actually incorrect. PR https://github.com/juju/juju/pull/11511 incorporates the changes from 11500 (+ some minor fixes) and properly enables instance-type constraints with space characters.

With this fix the bootstrap command now becomes (note: no escape needed):

```juju bootstrap rackspace/lon ctrl --bootstrap-constraints instance-type=4GB Standard Instance```

[Achilleas Anagnostopoulos (achilleasa)]

After discussing the caveats for the solution that landed with PR #11500, we decided to go for a more streamlined solution (escape spaces with slashes) that retains the validation logic (don't allow the operator to specify the same constraint type more than once) from the original code and will land https://github.com/juju/juju/pull/11519 as a followup fix.

With the followup fix the bootstrap command now becomes:

juju bootstrap rackspace/lon ctrl --bootstrap-constraints instance-type=4GB\ Standard\ Instance