Change dto for page blog documents to access fields in safe manner

[artem-shelkovnikov]

Minor change to replace unsafe object field access with safe one - we've received reports with errors coming from these lines because some intermediate objects were None:

Traceback (most recent call last):
  File "/app/connectors/sources/confluence.py", line 1154, in _page_blog_coro
    async for document, attachment_count, space_key, permissions, restrictions in self.fetch_documents(
  File "/app/connectors/sources/confluence.py", line 904, in fetch_documents
    "author": document["history"]["createdBy"][self.authorkey],
KeyError: 'publicName'
[FMWK][18:00:15][ERROR] Exception found for task Task-132
Traceback (most recent call last):
  File "/app/connectors/sources/confluence.py", line 1154, in _page_blog_coro
    async for document, attachment_count, space_key, permissions, restrictions in self.fetch_documents(
  File "/app/connectors/sources/confluence.py", line 904, in fetch_documents
    "author": document["history"]["createdBy"][self.authorkey],
KeyError: 'publicName'

Checklists

Pre-Review Checklist

• this PR does NOT contain credentials of any kind, such as API keys or username/passwords (double check config.yml.example)
• this PR has a meaningful title
• this PR links to all relevant github issues that it fixes or partially addresses
• if there is no GH issue, please create it. Each PR should have a link to an issue
• this PR has a thorough description
• Covered the changes with automated tests
• Tested the changes locally
• Added a label for each target release version (example: v7.13.2, v7.14.0, v8.0.0)

Release Note

Fix Confluence connector not downloading some blog post documents due to unexpected response format.

[jedrazb]

Nice! 🚢

[github-actions]

💔 Failed to create backport PR(s)

Status	Branch	Result
✅	8.x	#2986
✅	8.16	#2987
❌	8.15	Commit could not be cherrypicked due to conflicts

Successful backport PRs will be merged automatically after passing CI.

To backport manually run:
backport --pr 2984 --autoMerge --autoMergeMethod squash

[artem-shelkovnikov]

💚 All backports created successfully

Status	Branch	Result
✅	8.15

Note: Successful backport PRs will be merged automatically after passing CI.

Questions ?

Please refer to the Backport tool documentation