Issue403 dhc development - merged with new Aixlib Main Branch and work on adding the models for District heating and cooling

[rahul-karuvingal]

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Please consider these points before submitting:

• Mention the issue that this Pull Request intends to solve, and briefly describe what the main changes are.
• Make sure all new code follows our Modelica Guidelines
• Make sure all new models include documentation as described in the Documentation Wiki-Page and are demonstrated by suitable examples

If you know someone who could review your code, please use the Reviewer function on the right to ask for a review and also assign the PR to them. If not, no worries, we will find someone for you.

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[ebc-aixlib-bot]

Thank you for making a Pull Request to AixLib!

Our CI pipeline will help you finalize your contribution.
Here's what is typically checked:

• HTML syntax of your models, primarily in your documentation.
• Adherence to the naming convention in all changed files.
• Ability to check all models.
• Ability to simulate all models, if they are examples.
• If your contribution changes existing reference results.

If HTML errors occur, I will fix the issues using a separate pull request.
For the other checks, I will post the results here: https://rwth-ebc.github.io/AixLib/issue403_dhc_development/index.html

Tips to fix possible naming violations:

• Stick to the naming guidelines, e.g. Namespace Requirements
• Do all paramaters, variables, models, etc. have a description?
• Use absolute paths to classes! -> AixLib.Fluid.HeatExchangers.Radiator - Avoid: HeatExchangers.Radiator

If all CI stages pass and you have addressed possible naming violations, please consider the following:

• Use "group" and "tab" annotations to achieve a good visualization window.
• Use units consistently.
• Instantiate the replaceable medium package as:
  replaceable package Medium = Modelica.Media.Interfaces.PartialMedium "Medium model";
  instead of using a full media model like AixLib.Media.Water directly.
• Never using absolute paths to files (e.g., C: or D:). Replace them with modelica://AixLib/....
• Ensure your documentation is helpful and concise.
• Make sure icons are clear. Please avoid using images!
• Stick to 80 characters per line, as long as it makes sense.
• Add or modify examples for new or revised models.
• Include a simulate-and-plot script as a regression test for new models.
  How? Follow the documentation here: https://github.com/ibpsa/modelica-ibpsa/wiki/Unit-Tests#how-to-include-models-as-part-of-the-unit-tests
  Tip: To create the initial script, you can use Dymolas script generator, explained here: https://www.claytex.com/tech-blog/how-to-use-a-plot-script/)

Once you have addressed these points, you can assign a reviewer.
Although this process may seem tedious, ensuring CI passes allows the reviewer to focus
their time on the actual modeling rather than syntax and unintended breakages caused by your changes.

If you have any questions or issues, please tag a library developer.
Once again, thank you for your valuable contribution!