Fix grafana_user password idempotency

This commit fixes the issue that on each puppet run the user password
will be set.  As the grafana API does not provide any feature for that
we try to connect as that user if login works we suppress the password
change.

Fixes voxpupuli#104

lib/puppet/provider/grafana_user/grafana.rb

@@ -82,7 +82,7 @@ def theme=(value)
   end
 
   def password
-    user[:password]
+    nil
   end
 
   def password=(value)
@@ -126,6 +126,24 @@ def save_user
     self.user = nil
   end
 
+  def check_password
+    uri = URI.parse format('%s://%s:%d%s/dashboards/home', grafana_scheme, grafana_host, grafana_port, resource[:grafana_api_path])
+    request = Net::HTTP::Get.new(uri.to_s)
+    request.content_type = 'application/json'
+    request.basic_auth resource[:name], resource[:password]
+    response = Net::HTTP.start(grafana_host, grafana_port,
+                               use_ssl: grafana_scheme == 'https',
+                               verify_mode: OpenSSL::SSL::VERIFY_NONE) do |http|
+      http.request(request)
+    end
+
+    if response.code == '200'
+      true
+    else
+      false
+    end
+  end
+
   def delete_user
     response = send_request('DELETE', format('%s/admin/users/%s', resource[:grafana_api_path], user[:id]))
 

lib/puppet/type/grafana_user.rb

@@ -43,6 +43,9 @@
 
   newproperty(:password) do
     desc 'The password for the user'
+    def insync?(_is)
+      provider.check_password
+    end
   end
 
   newproperty(:email) do