Unify abstract and section paragraphs

[jankrepl]

We should be able to assign an embedding to the abstract. However, currently the abstract is a separate field/attribute of the Article class.

Todos

• Decide on the best design
• Implement it

Some reference

• Integrate abstract into sentences table #593

[FrancescoCasalegno]

Planning 2022-09-27

Discussion

• We want the article-to-json process to be reversible.
• So it will be responsibility of the json-to-elasticsearch process to upload also the article abstracts into the paragraphs table.
• To go back to the json from the elasticsearch we will just need to ignore the abstract entries.