fix: datasets documents update-by-file api missing assign field 'indexing_technique' internally

[StrayDragon]

Summary

when post /datasets/{dataset_id}/documents/{document_id}/update-by-file with only name and file filed, i got error:

{
  "code": "invalid_param",
  "message": "1 validation error for KnowledgeConfig\nindexing_technique\n  Field required [type=missing, input_value={'doc_form': 'text_model'...45c5-b58f-642ae837a9b9'}, input_type=dict]\n    For further information visit https://errors.pydantic.dev/2.9/v/missing",
  "status": 400
}

this pr fix this problem just like

dify/api/controllers/service_api/dataset/document.py

Lines 146 to 147 in 7790214

	# indexing_technique is already set in dataset since this is an update
	args["indexing_technique"] = dataset.indexing_technique

do

to fix #14266

Screenshots

see Summary

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[StrayDragon]

hey, I just checked the contribution guidelines. @guchenhe @crazywoola seem to be the right fit for this PR.

Not sure if you're free to check my PR. If it works for you, would you mind giving it a look?

Thank you!

[crazywoola]

@StrayDragon Please open an issue or link an existing issue in the description.

[StrayDragon]

@StrayDragon Please open an issue or link an existing issue in the description.

ok, i have created a new issue ( #14266 ) after searched exist issues.
Please deal with it when you have time. Thank you!