…igSecret

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_<endpoint>_<key> .
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 <service>-config-data secret of the service like:
$ oc get secret -n openstack neutron-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:[email protected]/keystone?read_default_file=/etc/my.cnf
KeystoneEndpointInternal: https://keystone-internal.openstack.svc:5000
KeystoneEndpointPublic: https://keystone-public-openstack.apps-crc.testing
TransportURL: rabbit://user:[email protected]:5671/?ssl=1
VHosts:
    internal:
        Override: false
        SSLCertificateFile: /etc/pki/tls/certs/internal.crt
        SSLCertificateKeyFile: /etc/pki/tls/private/internal.key
        ServerName: neutron-internal.openstack.svc
        TLS: true
    public:
        Override: false
        SSLCertificateFile: /etc/pki/tls/certs/public.crt
        SSLCertificateKeyFile: /etc/pki/tls/private/public.key
        ServerName: neutron-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

Signed-off-by: Martin Schuppert <[email protected]>