## Description
Telegram inbound attachments were stored under a generic, renamed
filename (e.g. `file_5.pdf`) instead of the name the sender actually
uploaded (e.g. `Quarterly-Report-2025.pdf`).
**Root cause:** In `Telegram::IncomingMessageService#attach_files`, the
attachment filename was taken from the `Down`-downloaded file's
`original_filename`, which `Down` derives from the Telegram file-server
download URL. That URL is built from Telegram's `getFile` response,
whose `file_path` is Telegram's *internal* storage path — not the
sender's chosen name. The real name is present in the webhook payload as
`file_name` on the `document` / `audio` / `video` object, but it was
never read.
Because `Attachment#set_extension` derives the stored `extension` from
the filename, this also corrupted the recorded extension for documents
whose Telegram path lacked a proper one.
**Fix:** Prefer the payload's `file_name`, falling back to the
downloaded name when it's absent (photos, stickers, voice notes — which
Telegram sends without a `file_name`). This mirrors how the Line channel
(`message['fileName']`) and WhatsApp Cloud channel already handle
inbound attachment filenames.
```ruby
filename: file[:file_name].presence || attachment_file.original_filename,
```
Fixes#15070
## Type of change
- [x] Bug fix (non-breaking change which fixes an issue)
## How Has This Been Tested?
Added/updated specs in
`spec/services/telegram/incoming_message_service_spec.rb`:
- Extended the existing document-message example to assert the stored
attachment retains the original payload filename (`Screenshot 2021-09-27
at 2.01.14 PM.png`) rather than Telegram's internal download name.
- Added a fallback example (a `photo` payload, which carries no
`file_name`) asserting the attachment is still created and the filename
falls back to the downloaded name — guarding the `.presence || …` branch
and confirming no regression for media types without a `file_name`.
> Note: my local machine does not have the Ruby/Redis toolchain to run
the suite, so I have not run RSpec/RuboCop locally — I'm relying on CI
to validate. Suggested command for reviewers: `bundle exec rspec
spec/services/telegram/incoming_message_service_spec.rb`.
## Checklist:
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] I have commented on my code, particularly in hard-to-understand
areas
- [x] I have added tests that prove my fix is effective
- [ ] New and existing unit tests pass locally with my changes (unable
to run locally — see note above; relying on CI)
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