Add Attachments PDF or Image from api.py request about wekan

[xet7]

@xator91

Database structure. Also other models files have REST API for text-based data. There is attachment storage strategy pattern (like in Java), how to use files at MongoDB GridFS, filesystem or S3/Minio, and some moving attachments code, but it currently only uses files from MongoDB.

https://github.com/wekan/wekan/blob/main/models/attachments.js

https://github.com/wekan/wekan/blob/main/models/lib/attachmentStoreStrategy.js

https://github.com/wekan/wekan/blob/main/client/components/cards/attachments.js

At cards, attachments are uploaded:

https://github.com/wekan/wekan/blob/main/client/components/cards/attachments.jade

https://github.com/wekan/wekan/blob/main/client/components/cards/attachments.css

At Admin Panel is list of attachments:

https://github.com/wekan/wekan/blob/main/client/components/settings/attachments.js

https://github.com/wekan/wekan/blob/main/client/components/settings/attachments.jade

https://github.com/wekan/wekan/blob/main/client/components/settings/attachments.css

List of files at current board is published from serverside MongoDB database to browserside Javascript-based minimongo database, with realtime updates, based on newest changes that Meteor Javascript web framework reads from MongoDB change stream:

https://github.com/wekan/wekan/blob/main/server/publications/attachments.js

Currently exporting board to JSON is missing attachments, that previously (before changing from CollectionFS to Meteor-Files way to store files with GridFS to MongoDB database) were included as base64 encoded to JSON file, but it needs checking are attachments included:

https://github.com/wekan/wekan/blob/main/client/components/sidebar/sidebar.js#L263

base64 code maybe here:

https://github.com/wekan/wekan/blob/main/models/exporter.js#L48

That sidebar export options are at board: click right top hamburger menu / Board Settings / Export Board. There is:

• JSON, that is WeKan board as JSON file, but it does not have attachments currently. Also, exporting big board maybe timeouts sometime.
• HTML, exporting WeKan board as .zip file where is HTML static webpage, images etc. In theory, attachments from board could be added, but I don't know how it would work with big amount of attachments.
• Excel XLSX, that uses npm package exceljs at package.json of https://github.com/wekan/wekan , adding text to spreadsheet cells at https://github.com/wekan/wekan/blob/main/models/exportExcel.js and https://github.com/wekan/wekan/blob/main/models/server/ExporterExcel.js