Implement a template format where a specific list of structures can be specified with corresponding relative locations

[GregSal]

Create a custom_diagram_layout dataclass in the diagram_layout module with the following structure:

{
    "template_name": "Template Name",
    "template_description": "Template Description",
    "template_version": "1.0",
    "template_author": "Author Name",
    "template_date": "2024-06-01",
    "template_layout": {
        "Structure ID 1": {
            "x": 0,
            "y": 0
        },
        "Structure ID 2": {
            "x": 1,
            "y": 0
        },
        ...
    }
}

Then create functions in the module to load the templates from a Jason file,
validate the templates and make them accessible via the existing
get_layout_template function. As part of this, create a public function to add new templates
to the existing templates referenced by the get_layout_template function. The function to add new templates should accept a template definition as a dictionary in the above format and add it to the existing templates.

Finally, in the Custom Diagram Layout The diagram rendering function will use the existing render_template_diagram
function to render the diagram based on the loaded template.

A Custom Diagram Layout Template is defined by a data structure that specifies
the Structure and its relative location on the diagram. The templates are
"Custom" because their definition can be stored in a Jason file and loaded into
the program. This allows for the creation of new templates without having to
modify the code.

The definition is in the following format:

In the initial implementation only an exactly matching "Structure ID" will be
accepted.

[GregSal]

In the future I will want to expand this to include the use of wildcards or
regex patterns, but I do not want to implement this now because it will require
dealing with multiple matches. I may also want to allow the structure matching
to reference other attributes of the structure such as the "Structure Type" or
"Density".

At that point I will need additional parameters:

1. An indicator as to how to treat the text i.e. literal or regex
2. An indicator of the structure attribute to match against (e.g. Structure ID, Structure Type, Density, etc.)
3. A parameters to indicate what to do with multiple matches

• One possibility here is a "Distribute vertical" or
  "Distribute Horizontal" option. This would specify that multiple
  matches should be centered around the specified coordinates
  but distributed in the specified direction.
• If I do this I might also want a spacing factor for the distribution.
• In terms of the overall relative coordinates, they would have to take
  into account the size of the block of nodes when converting
  relative coordinates into absolute ones.

[GregSal]

Eventually these layout patterns would be stored in a Json file