docs: How to create a new grant (#1002)

docs(devel): How to create a new grant

* documentation about how grants system works and references about how to do a test for it.
* docs: add clarification about pci-stubs ( issue #742 )

issue  #996

docs/devel-docs/create_grants.rst

+How to create a new grants
+========================
+
+If you want to add a new grant, you have to do two things:
+
+    -  Add the grant and enable it in to the BD
+    -  Add the condition
+    
+You can see all the grants in the table 'grants_type', to add it automatically on start up the
+backend you have to modify the functions ``_add_grants`` and `` _enable_grants`` in the file "lib/Ravada.pm"
+
+Now the test file is like this:
+
+::
+    
+    ...
+    
+    sub _add_grants($self) {
+    #   How to
+    #   $self->_add_grant('grant_name', enable/disable by default, "description")
+
+    #   Examples
+        $self->_add_grant('shutdown', 1,"Can shutdown own virtual machines");
+        $self->_add_grant('start_many',0,"Can have more than one machine started")
+    }
+    ...
+    sub _enable_grants($self) {
+    ...
+    my @grants = (
+        # How to
+        # 'grant_name'
+        
+        # Examples
+        'change_settings',  'change_settings_all',  'change_settings_clones'
+        ,'clone',           'clone_all',            'create_base', 'create_machine'
+        ,'grant'
+        ,'manage_users'
+        ,'remove',          'remove_all',   'remove_clone',     'remove_clone_all'
+        ,'screenshot'
+        ,'shutdown',        'shutdown_all',    'shutdown_clone'
+        ,'screenshot'
+        ,'start_many'
+    );
+    ...
+    
+Next for adding the conditions it depends of the situations but you may want to lock in to thins functions:
+
+    -  "templates/main/settings_machine_tabs_head.html.ep" & "templates/main/settings_machine_tabs_head.html.ep" for Virtual Machine edit settings web page.
+    -  "lib/Ravada/Auth/SQL.pm" all the grants conditions created (i.e. ``is_admin``, ``can_list_clones``, etc...).
+    
+**Note**:If the function is named ``can_'grant_name'`` this function is automatically generated with the BD data.
+
+Testing
+-------
+
+Some examples for testing can be found in "/t/user/50_admin.t" and "/t/user/40_grant_shutdown.t" also you may want to read the section **How to create tests**. 

docs/docs/gpu.rst

@@ -33,7 +33,8 @@ To enable SR-IOV in the kernel add any of these following options for pass-throu
 	GRUB_CMDLINE_LINUX_DEFAULT="radeon.blacklist=1 quiet splash amd_iommu=on pci-stub.ids=1002:6608,1002:aab0"
 	GRUB_CMDLINE_LINUX_DEFAULT="radeon.blacklist=1 amdgpu.blacklist=1 quiet splash intel_iommu=on amd_iommu=on iommu=pt rd.driver.pre=vfio-pci video=efifb:off pci-stub.ids=1028:2120,1028:aab0"
 
-Add pci-stubs in ``/etc/initramfs-tools/modules``.
+Add pci-stubs in ``/etc/initramfs-tools/modules``, just add this line: ``pci-stub ids=1002:6608,1002:aab0;``. 
+
 Then add these additional drivers to ``/etc/modules``:
 
 ::