feat(aws_tools): add S3 File Uploader and S3 File Download tools

[leoou331]

What this PR does

Adds two new builtin tools to the aws_tools plugin:

• s3_file_uploader — takes a file variable from an upstream workflow node (Start file input, LLM output, another tool, etc.) and uploads it to a configurable S3 bucket/key. Optionally returns a presigned GET URL.
• s3_file_download — takes an s3://bucket/key URI and emits the object as a Dify file (via create_blob_message) plus structured metadata for downstream nodes.

Why

The existing s3_operator is text-only:

• input is text_content: string
• output is UTF-8 decoded string

It cannot be wired to a Start node's file input, nor consume the file output of nodes like Frame Extractor / Nova Canvas. These two new tools close that gap and keep the same UX as the rest of the plugin (provider-level credentials, optional per-tool overrides, three-language labels).

A typical workflow now looks like:

[Start: file input] -> [s3_file_uploader] -> ... -> [s3_file_download] -> [LLM/Code/...]

Files

plugins/aws_tools/
├── provider/aws_tools.yaml           # +2 lines (register both tools)
└── tools/
    ├── s3_file_uploader.py           # 201 lines
    ├── s3_file_uploader.yaml         # 139 lines
    ├── s3_file_download.py           # 175 lines
    └── s3_file_download.yaml         # 78 lines
README.md, README_ZH.md, README_JA.md # +2 lines each (tool table)

Both Python modules are self-contained — credential-resolution helpers (_resolve_aws_credentials, _build_boto3_client_kwargs, _reset_clients_on_credential_change) are inlined so this PR does not introduce a shared utils/ module that the rest of the repo doesn't use.

Tool surface

s3_file_uploader (form parameters)

Param	Type	Required	Notes
input_file	file	yes	Bound to upstream file variable.
bucket_name	string	yes	Without s3://.
key_prefix	string	no	Folder-style prefix, e.g. workflow-outputs.
object_key	string	no	Override final key; defaults to incoming filename.
aws_region	string	no	Per-tool override of provider default.
aws_access_key_id / aws_secret_access_key / aws_session_token	string	no	Per-tool override / STS support.
generate_presign_url	boolean	no	Default false.
presign_expiry	number	no	Default 3600 seconds.

Outputs three messages: text = s3://bucket/key or presigned URL; json = {bucket_name, object_key, s3_uri, presigned_url?, presign_expiry?}; no files.

s3_file_download

Param	Type	Required	Notes
s3_uri	string (LLM-fillable)	yes	s3://bucket/key.
aws_region / aws_access_key_id / aws_secret_access_key / aws_session_token	string	no	Same overrides as uploader.

Outputs files = [<Dify file>], json = {bucket, key, content_type, content_length, etag, last_modified, s3_uri}, and a key=value text block of the same metadata.

Validation

Static:

• python -m py_compile on both .py files — ✅
• yaml.safe_load on both new yaml files and the modified provider/aws_tools.yaml — ✅
• Verified extra.python.source paths resolve to existing files — ✅
• Confirmed label/description languages match the rest of the plugin (en_US / zh_Hans / pt_BR) — ✅

End-to-end (this is from a real run, not a dry validation):

1. Built a .difypkg from plugins/aws_tools/ on this branch.
2. Installed it on a self-hosted Dify 1.14.2 Community Edition.
3. Imported a workflow [Start (file input) -> s3_file_uploader -> s3_file_download -> End], pointed at S3 bucket in cn-northwest-1.
4. Triggered the workflow via the Service API with hello.txt (244 bytes).
5. Result:
   • status = succeeded, total_steps = 4, elapsed = 1.0s
   • uploaded_uri = s3://dify-test-s3-function/pr-validation/hello.txt
   • downloaded_meta populated with bucket / key / content_type / content_length=244 / etag / last_modified / s3_uri
6. Pulled the object back from S3 with aws s3 cp and compared SHA-256 — byte-for-byte identical with the local source.

Out of scope

• Multipart upload / streaming for large files
• Any change to existing s3_operator behavior
• Shared utils/ module — left for a follow-up if more tools want the helpers

[leoou331]

Pushed 546e2a3 to mirror review fixes from the upstream langgenius PR (langgenius/dify-official-plugins#3273):

1. Drop cached self.s3_client; build a local boto3 client per _invoke call (removes a thread-safety / cross-tenant credential-leak risk).
2. Remove the now-unused _reset_clients_on_credential_change / _credential_signature helpers (-23 lines).
3. Use standard ClientError error-code matching for NoSuchBucket / NoSuchKey in s3_file_download (no longer depends on the cached client's .exceptions namespace).
4. Tolerate trailing slashes in the S3 key when deriving the downloaded filename.
5. Safe presign_expiry parsing (None / "" / non-numeric all fall back to 3600 instead of TypeError).

Re-validated end to end on Dify 1.14.2: TXT / PNG / PDF / presign URL / STS aws_session_token paths all succeed; SHA-256 byte-for-byte identical on every round-trip.