Improve ECS documentation

[AlexRuiz7]

Description

Currently, our documentation for the indices and index templates are hosted in ecs/docs in Markdown format. Although this was useful during the first steps of the development of the Data Persistence Model redesign objective, it requires strong maintenance work each time we add any change to the indices. However, the ECS generator tool generates, along the index templates, CSV files that we can use as documentation. By including these files to the repository, and by adapting the ECS generator automation scripts and workflow, we can fully automate the generation of the indices templates and the documentation.

Functional requirements

• The documentation for the indexes are generated automatically.
• The documentation is updated each time an index definition is changed.
• The documentation is in CSV format.

Implementation restrictions

• Extend the existing automation to build the documentation.

Plan

• Create a sub-folder for each of the indices. Within each folder, there is a README.md with basic information about the index a fields.csv file.
• Update the automation to update the fields.csv accordingly on changes.
• Clear the ecs/docs folder.