Fix transaction names for starlette Mount routes

[pypae]

What does this pull request do?

Fix transaction names for starlette Mount routes.
Recursively build route names for mounted sub-applications.

Related issues

closes #1036

Note: Opened it as a draft pull request because I couldn't write tests yet, but I still wanted to give you an idea of a potential fix.

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Build stats

• Build Cause: Pull request #1037 updated

• Start Time: 2021-02-19T18:54:22.296+0000

• Duration: 21 min 15 sec

• Commit: 06c6d75

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Failed	0
Passed	7947
Skipped	5735
Total	13682

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Test stats 🧪

Test	Results
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Passed	7947
Skipped	5735
Total	13682

[beniwohli]

@pypae great work on the fix! I had a look at the issue that you opened yesterday and came to the same conclusion that a recursive approach is probably the cleanest. I don't expect these hierarchies of mounts to become very deep, so the overhead of recursion over an iterative approach should be fairly small.

I took the liberty to push a test I wrote yesterday to confirm the issue to your branch.

[beniwohli]

Great work, thanks!

[pypae]

I just realized that naming for trailing slash redirects does not work correctly with sub-applications.
On another note: Are you okay with the nested and untyped function _get_route_name, or should I move it?

Thank you for this awesome project by the way.

[basepi]

Are you okay with the nested and untyped function _get_route_name, or should I move it?

I don't necessarily have a problem with it, but since it's not a closure it would probably be cleaner to make it a separate method.