feat: Add warning for no api

[Reillyhewitson]

This PR will close #380

Description

Added a check to the configuration file loading function that outputs a warning if it cannot find a section for datagateway or search api in the config file

Testing Instructions

Add a set up instructions describing how the reviewer should test the code

• Review code
• Check GitHub Actions build
• If icatdb Generator Script Consistency Test CI job fails, is this because of a deliberate change made to the script to change generated data (which isn't actually a problem) or is here an underlying issue with the changes made?
• Review changes to test coverage
• Does this change mean a new patch, minor or major version should be made? If so, does one of the commit messages feature fix:, feat: or BREAKING CHANGE: so a release is automatically made via GitHub Actions upon merge?
• {more steps here}

Agile Board Tracking

Connect to #380

[codecov]

Codecov Report

Base: 94.48% // Head: 94.48% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (7dee9f6) compared to base (40197b2).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #386   +/-   ##
=======================================
  Coverage   94.48%   94.48%           
=======================================
  Files          39       39           
  Lines        3116     3118    +2     
  Branches      311      312    +1     
=======================================
+ Hits         2944     2946    +2     
  Misses        144      144           
  Partials       28       28           

Impacted Files	Coverage Δ
datagateway_api/src/common/config.py	100.00% <100.00%> (ø)

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[MRichards99]

Could you also print the same message please? It's good to have it in the logs, but a developer might be able to resolve an issue more quickly if the message is printed (as well as logged) rather than wondering what's going on, looking in the logs then finally realising their mistake.

[Reillyhewitson]

Logging seems to output the message during startup as well. If I add a print statement then I see the message twice. See my console output below

[root@localhost datagateway-api]# poetry run python -m datagateway_api.src.main
   WARNING: There is no API specified in the configuration file
   WARNING: There is no API specified in the configuration file
 * Serving Flask app 'main' (lazy loading)
 * Environment: production
   WARNING: This is a development server. Do not use it in a production deployment.
   Use a production WSGI server instead.
 * Debug mode: off

[MRichards99]

Ah ok, I didn't notice that! Looks good then, I'll approve