Add 'host' field to the custom resource

[avisiedo]

As an administrator I want to set the host from the custom resource that meet with:

• If it is not specified, the default value is filled to ".".
• If the value is longer than 64 chars the CR is rejected and the CR is not stored in etcd.
• If it is not a valid host string, the CR is rejected.
• The value is passed to the container as IPA_SERVER_HOSTNAME environment variable.
• The value is mapped to the Route.Spec.Host field for the Route object.

[frasertweedale]

I'm not sure if this is the right thing to do. An IDM CR would be for a whole deployment, probably consisting of multiple servers. If it helps with any kind of demo situation right now, then I'm OK to merge it. Just wanted to point out that it's almost certainly going to have to change again.

Alternatively, we could auto-generate the server names for each replica, using the realm or IDM domain as the DNS suffix.

[frasertweedale]

@avisiedo pointed out that this PR also adds validation to ensure hostname does not exceed 64 chars. This is useful right now, so we can merge this PR. And later we will have to change it to allow specifying a "base domain" in the CR, and create IDM server domain names (for individual replicas) as children of that domain.

[openshift-ci[bot]]

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This pull-request has been approved by: avisiedo, frasertweedale

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