set default file ID manager to arbitrary

[dlqqq]

Per discussion with Jupyter server team, it is the consensus that LocalFileIdManager is not yet ready for mainstream use. Hence we are setting the default file ID manager to be ArbitraryFileIdManager regardless of the current contents manager.

[dlqqq]

cc @kevin-bates @davidbrochart

[codecov-commenter]

Codecov Report

Base: 81.43% // Head: 83.24% // Increases project coverage by +1.80% :tada:

Coverage data is based on head (6207f57) compared to base (71c90c6). Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #37 +/- ## ========================================== + Coverage 81.43% 83.24% +1.80% ========================================== Files 5 5 Lines 544 549 +5 Branches 71 69 -2 ========================================== + Hits 443 457 +14 + Misses 79 71 -8 + Partials 22 21 -1 ``` | [Impacted Files](https://codecov.io/gh/jupyter-server/jupyter_server_fileid/pull/37?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jupyter-server) | Coverage Δ | | |---|---|---| | [jupyter\_server\_fileid/extension.py](https://codecov.io/gh/jupyter-server/jupyter_server_fileid/pull/37/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jupyter-server#diff-anVweXRlcl9zZXJ2ZXJfZmlsZWlkL2V4dGVuc2lvbi5weQ==) | `44.00% <100.00%> (+6.50%)` | :arrow_up: | | [jupyter\_server\_fileid/manager.py](https://codecov.io/gh/jupyter-server/jupyter_server_fileid/pull/37/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jupyter-server#diff-anVweXRlcl9zZXJ2ZXJfZmlsZWlkL21hbmFnZXIucHk=) | `91.17% <0.00%> (+1.12%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jupyter-server). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=jupyter-server)

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[kevin-bates]

Per discussion with Jupyter server team, it is the consensus that LocalFileIdManager is not yet ready for mainstream use.

I'm not sure this is quite correct. I recall expressing a concern that being so closely tied to the filesystem was going to be problematic due to the wide variety of filesystems. And there seemed to be some consensus that using a mechanism like watchdog or watchfiles might be more useful since they know filesystems (or at least filesystem idiosyncracies would be "their problem"). But I don't recall a consensus that LocalFileIdManager was not ready for mainstream use - heck, it's still in its infancy.

That said, it does sound like RTC's usage is increasing, and a release is looming, so I think having a fallback in the ArbitraryFileIdManager may be a good idea.

[dlqqq]

@kevin-bates That was the impression I got from @ellisonbg. @ellisonbg Could you offer your thoughts on this?