Custom, extensible needflow

[danwos]

Currently needflow draws everything based on a given filter.
But there are scenarios, where a user wants to manipulate or extend this drawing, before it gets finally realized in the documentation.

Use cases are:

• Add hints to specific needs
• Set own links between needs
• Add single needs (could be done by adding a "... id=='NEED_ID'" to the filter, but there must be easier ways)
• Build own views of need objects.

You can do all this already, by just using planutml and define a picture completely by hand.
But there must be easier, more stable and reliable ways to get it done.

So here is the idea:

Technical concept

Provide a new directive needuml, which content takes a PlantUML definition.
So it acts as the uml directive form sphinxcontrib.plantuml.

But it has some special features, which manipulates the given plantuml-code.

Ideas:

.. needuml::
  
   [[def(type=="req")]]
   [[def_list(ID_1, ID_123)]]

   [[links(type=="req")]]

   card "my_own_card" as my_card
   my_card -> ID_1

This gets "translated" to:

.. uml::

   ` Definitions from  [[def(type=="req")]]
   node "A requirement need" as ID_REQ_1
   node "Another requirement need" as ID_REQ_2
  
   ' Definition from [[def_list(ID_1, ID_123)]]
   node "Title of need ID_1"  as ID_1
   node "Title of need ID_123"  as ID_123

   ' Links from [[links(type=="req")]]
   ID_REQ_1 --> ID_REQ_2

   ' User defined content
   card "my_own_card" as my_card
   my_card -> ID_1

So the goal is to have some "functions" (like the dynamic functions), which create plantuml-valid code, which gets injected into the given
plantuml-code.

Ideas for functions:

• def(filter_string): Creates plantuml-objects based on filter_string
• def_list(list[]): Create plantuml objects based on given ID list
• **links(filter_string): Create links between plantuml-objects. Objects must be defined by user or ``def() in advance

For sure, all these functions could get some additional options:

• type: Define the used node type and don't take it from conf.py
• color
• link_type: Only connect plantuml-objects based provided link type

So I think there is room to implement a lot of ideas.

But lets starts with the basics for this tickets and just implement:

• The directive needuml
• The function-replacement mechanism
• The functions: def() and links()

[danwos]

Doable via needuml now