Describe the bug
After #8681 has been added, a new popup is being opened to add several images (attachments). That pop-up allows you to change the name of the attachment. After editing the pictures and submitting the form, the chosen name is not taken into account.

To Reproduce
Steps to reproduce the behavior:

1. Login in the application
2. Go to a new proposal form (inside any participatory space )
3. Fill in the required details for a proposal
4. click on Add images, upload and change the title to anything else than Default title
5. Save the Attachments, and proposal
6. In the preview screen observe the image's alt text

Expected behavior
I would like to have the added name in the upload form to be taken into account when listing the image. After uploading the picture, the alt text should be the text filled in the previous screen (as per attached images the Text should be "Meow picture", yet the displayed one is "Screenshot from 2022-03-03 14-2")

Screenshots

Stacktrace
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Extra data (please complete the following information):

• Device: Firefox
• Device OS: Ubuntu 20.04-LTS
• Browser: Firefox 98.0 (64-bit)
• Decidim Version: 0.27-dev
• Decidim installation: Future of Europe

Additional context
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