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**Related issue:** Resolves#40519
# Details
This PR adds a new system for registering deprecated URLs separately
from the main URLs (i.e. not clogging up `handler.go` with a bunch of
`.WithAltPaths()` or similar. It uses a registry that's shared between
all the different endpointer, which is then iterated over and a new
handler is created for the deprecated endpoint which stores info about
the deprecation (the old and new URLs) in the context. A new middleware
looks for that context info and, if found, logs a deprecation warning
(if the topic is enabled).
# Checklist for submitter
If some of the following don't apply, delete the relevant line.
- [ ] Changes file added for user-visible changes in `changes/`,
`orbit/changes/` or `ee/fleetd-chrome/changes`.
See [Changes
files](https://github.com/fleetdm/fleet/blob/main/docs/Contributing/guides/committing-changes.md#changes-files)
for more information.
no need for a changelog as we are not logging the warnings by default
## Testing
- [X] Added/updated automated tests
- [X] QA'd all new/changed functionality manually
* Verified that going to `/teams` with
`--logging_enable_topics=deprecated-field-names` got me this log:
```
deprecated_path=/api/_version_/fleet/teams deprecation_warning="API `/api/_version_/fleet/teams` is deprecated, use `/api/_version_/fleet/fleets` instead
```
* Going to `/fleets` with that flag enabled resulted in no deprecation
log
* Going to `/teams` _without_ the flag enabled resulted in no
deprecation log
