API : update a namespace's metadata and role mappings

[pierrotsmnrd]

This PR adds a new API endpoint to update a namespace's role mappings and metadata.

the PUT /conda-store/api/v1/namespace/{namespace}/ endpoint takes a JSON payload to update the metadata, the role mappings, or both.

• update the metadata :

{
  "metadata": {"my_key":"my_value"}
}

• update the role mappings :

{
  "role_mappings": {
    "admin/admin": ["admin", "viewer", "developer"],
    "admin/*": ["viewer"],
    "demo/*": ["developer"]
  }
}

• update both :

{
  "metadata": {"my_key":"my_value"},
  "role_mappings": {
    "admin/admin": ["admin"],
    "admin/*": ["viewer"],
    "demo/*": ["developer"]
  }
}

@costrouc tell me if that works for you or if you'd see another approach or pattern.

According to the original issue #491 :

• namespace update rest api method that uses the namespace update
• create, list, delete for adding namespace role mappings. I think you should only be able to edit namespace role mappings if you have namespace::update permissions. If you have namespace::read it should be sufficient to view members.

We now need to add an endpoint to list the role mappings.

[costrouc]

@pierrotsmnrd this PR looks great to me. No real issues. My questions is on the granularity of permissions:

Should we have one permission namespace::update or should we have more? I think it is always easier to join permissions than to split them later on. Roles already provide an easy way to group them. To me having the ability to change a namespaces metadata and giving users permissions to a namespace are at much different permission levels.

So for example:

• namespace::update update the metadata for a namespace
• namespace-role-mapping::read
• namespace-role-mapping::create
• namespace-role-mapping::delete

I'm not entirely sure on the naming. This would allow us to give people viewer access to namespaces but not see who else is a member etc. Not sure if there is an exact use case for now but it could be useful to give people view access to a namespace but not see who is there.

[costrouc]

Let's not use | since this isn't backwards compatible with 3.9. Use typing.Union

[costrouc]

LGTM. Thanks @pierrotsmnrd