manageiq_provider: don't send top-level null fields on creation (#38448)

* manageiq_provider: method docstrings fixes

* manageiq_provider: refactoring step towards DRY

`resource` is now same in `edit_provider()` and `create_provider()`,
to be extracted to main later.

* manageiq_provider: Fix creation of openshift provider

Fixes #38331.
Sending `api_version` to openshift provider would cause error:
"OpenShift api_version cannot be modified"
due to https://github.com/ManageIQ/manageiq-providers-kubernetes/blob/gaprindashvili-2/app/models/manageiq/providers/kubernetes/container_manager.rb#L37

In `edit_provider` we `delete_nulls()` on the whole data being sent
so `api_version` was omitted if not specified.
In `create_provider()` we only did it on endpoints list so `api_version`
was always sent - now doing on whole data.

lib/ansible/modules/remote_management/manageiq/manageiq_provider.py

@@ -694,7 +694,7 @@ class ManageIQProvider(object):
     def edit_provider(self, provider, name, provider_type, endpoints, zone_id, provider_region,
                       host_default_vnc_port_start, host_default_vnc_port_end,
                       subscription, project, uid_ems, tenant_mapping_enabled, api_version):
-        """ Edit a user from manageiq.
+        """ Edit a provider from manageiq.
 
         Returns:
             a short message describing the operation executed.
@@ -737,22 +737,13 @@ class ManageIQProvider(object):
     def create_provider(self, name, provider_type, endpoints, zone_id, provider_region,
                         host_default_vnc_port_start, host_default_vnc_port_end,
                         subscription, project, uid_ems, tenant_mapping_enabled, api_version):
-        """ Creates the user in manageiq.
+        """ Creates the provider in manageiq.
 
         Returns:
-            the created user id, name, created_on timestamp,
-            updated_on timestamp, userid and current_group_id.
+            a short message describing the operation executed.
         """
-        # clean nulls, we do not send nulls to the api
-        endpoints = delete_nulls(endpoints)
-
-        # try to create a new provider
-        try:
-            url = '%s/providers' % (self.api_url)
-            result = self.client.post(
-                url,
+        resource = dict(
             name=name,
-                type=supported_providers()[provider_type]['class_name'],
             zone={'id': zone_id},
             provider_region=provider_region,
             host_default_vnc_port_start=host_default_vnc_port_start,
@@ -764,6 +755,14 @@ class ManageIQProvider(object):
             api_version=api_version,
             connection_configurations=endpoints,
         )
+
+        # clean nulls, we do not send nulls to the api
+        resource = delete_nulls(resource)
+
+        # try to create a new provider
+        try:
+            url = '%s/providers' % (self.api_url)
+            result = self.client.post(url, type=supported_providers()[provider_type]['class_name'], **resource)
         except Exception as e:
             self.module.fail_json(msg="failed to create provider %s: %s" % (name, str(e)))