[ENH] Make root_path for app configurable

[alyssadai]

• Closes Support subdirectory root paths when API is behind a proxy #152
• Related to: Add and document env vars for API root paths recipes#102

Changes proposed in this pull request:

• The root path for the FastAPI app is now configurable via an optional environment variable NB_FAPI_ROOT_PATH
  • Meant for use in deployment scenarios with proxy servers that use a stripped path prefix

Checklist

This section is for the PR reviewer

• PR has an interpretable title with a prefix ([ENH], [FIX], [REF], [TST], [CI], [MNT], [INF], [MODEL], [DOC]) (see our Contributing Guidelines for more info)
• PR has a label for the release changelog or skip-release (to be applied by maintainers only)
• PR links to GitHub issue with mention Closes #XXXX
• Tests pass
• Checks pass

For new features:

• Tests have been added

For bug fixes:

• There is at least one test that would fail under the original bug conditions.

Summary by Sourcery

Enhancements:

• Allow the application to be deployed under a specific path, such as /fapi/v1.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request introduces the ability to configure the root path for the FastAPI application, which is particularly useful when the application is behind a proxy. The root path is now configurable via the NB_FAPI_ROOT_PATH environment variable. Additionally, the interactive API documentation was updated to reflect the new root path.

Sequence diagram for API documentation access with configurable root path

sequenceDiagram
    actor User
    participant Browser
    participant API

    User->>Browser: Access API docs
    Browser->>API: GET {root_path}/docs
    Note over API: Uses configured root_path
    API->>Browser: Return Swagger UI HTML
    Note over Browser: Links use {root_path}/openapi.json
    Browser->>API: GET {root_path}/openapi.json
    API->>Browser: Return OpenAPI spec
    Browser->>User: Display API documentation

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File-Level Changes

Change	Details	Files
The application's root path is now configurable via the NB_FAPI_ROOT_PATH environment variable.	Added a new ROOT_PATH namedtuple to app/api/utility.py to store the root path from the environment variable. The FastAPI application is now initialized with the root_path parameter set to the value of the ROOT_PATH environment variable.	app/main.py app/api/utility.py
The interactive API documentation now correctly reflects the configured root path.	The /docs and /redoc endpoints now use the request.scope to dynamically generate the correct openapi_url based on the configured root_path. The root endpoint now uses the request.scope to dynamically generate the correct link to the API documentation based on the configured root_path.	app/main.py
Added tests to ensure the API documentation is accessible with the correct root path.	Added a new test case test_docs_work_using_defined_root_path to verify that the documentation is accessible with the correct root path. The test case uses monkeypatch to set the root_path attribute of the app object.	tests/test_routing.py

Assessment against linked issues

Issue	Objective	Addressed	Explanation
#152	Add environment variable for the root path	✅
#152	Set the root_path parameter when initializing FastAPI app	✅

Possibly linked issues

• Support subdirectory root paths when API is behind a proxy #152: The PR closes the issue by making the root path configurable, which enables support for subdirectory root paths.
• Support subdirectory root paths when API is behind a proxy #152: The PR closes the associated issue by making the root path configurable, which enables the addition of a welcome page.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.37%. Comparing base (af5e602) to head (fde6fe9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #154      +/-   ##
==========================================
+ Coverage   97.17%   97.37%   +0.20%     
==========================================
  Files          23       23              
  Lines         707      724      +17     
==========================================
+ Hits          687      705      +18     
+ Misses         20       19       -1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[surchs]

Looks good @alyssadai, one question about the trailing slashes.

Otherwise 🧑‍🍳