Support external annotations

[berombau]

Users should be able to add their own annotations, in the same format as the dataset, by using the Create annotation frontend and a folder. Basic support should include pngseq. The required code changes are:

backend

• schemas/annotation.py:AnnoationFileType: add pngseq = "pngseq"
• backend/app/app/api/api_v1/endpoints/utils.py:train_unet2d pass annotation filetype to celery task with new param annotation_filetype

frontend

• regenerate the code from the backend API as shown in the documentation. This should add the correct file types in the annotation form.

gpu_worker/app/worker.py:train_unet2d

• add new param annotation_filetype
• app/worker.py:train_unet2d Skip step Convert JSON annotations to .pngs if filetype is not json.

dash_frontend

• disable the edit annotation button if the type is not json.

Possible issues:

• The string representing location of the annotation will change from only a file annotations.json to either a file or a folder. This can break unknown stuff that depended on this assumption e.g. the annotation tools from the dash_frontend viewer or the folder creation in the gpu_worker.