Allow customize http vhost config using HttpdCustomization.CustomConfigSecret

[stuggi]

This change allows to customize the httpd vhost config using this parameter to specify a secret that contains service config data. The content of each provided snippet gets rendered as a go template and placed into /etc/httpd/conf/httpd_custom__ .
At the end of the vhost config in the default httpd template these custom configs get included using Include conf/httpd_custom_<endpoint>_*.

For information on how sections in httpd configuration get merged, check section "How the sections are merged" in https://httpd.apache.org/docs/current/sections.html#merging

All possible parameters which can be use in a template can be looked up in the -config-data secret of the service like:

$ oc get secret -n openstack manila-config-data -o json | jq -r .data.TemplateParameters | base64 -d

or in the running pod of the service in the file:

$ cat /var/lib/config-data/default/TemplateParameters

The content is a versioned dump of the parameters of the service operator, like:

DatabaseConnection: mysql+pymysql://user:pwd@openstack.openstack.svc/keystone?read_default_file=/etc/my.cnf
KeystoneInternalURL: https://keystone-internal.openstack.svc:5000 
KeystonePublicURL: https://keystone-public-openstack.apps-crc.testing 
TransportURL: rabbit://user:pwd@rabbitmq.openstack.svc:5671/?ssl=1
VHosts:
    internal:
        Override: false
        SSLCertificateFile: /etc/pki/tls/certs/internal.crt
        SSLCertificateKeyFile: /etc/pki/tls/private/internal.key
        ServerName: keystone-internal.openstack.svc
        TLS: true
    public:
        Override: false
        SSLCertificateFile: /etc/pki/tls/certs/public.crt
        SSLCertificateKeyFile: /etc/pki/tls/private/public.key
        ServerName: keystone-public.openstack.svc
        TLS: true
MemcachedServers: memcached-0.memcached.openstack.svc:11212 MemcachedServersWithInet: inet:[memcached-0.memcached.openstack.svc]:11211
...

Depends-On: openstack-k8s-operators/lib-common#591
Depends-On: openstack-k8s-operators/lib-common#593

Jira: https://issues.redhat.com/browse/OSPRH-13100

[openshift-ci]

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