Improve docker UX

[josecelano]

Some minor improvements to make using docker and the app configuration a smoother experience.

[codecov]

Codecov Report

Merging #367 (ec7bd7d) into develop (b09e95a) will decrease coverage by 0.06%.
Report is 1 commits behind head on develop.
The diff coverage is 4.16%.

@@             Coverage Diff             @@
##           develop     #367      +/-   ##
===========================================
- Coverage    85.07%   85.01%   -0.06%     
===========================================
  Files           88       89       +1     
  Lines         6564     6567       +3     
===========================================
- Hits          5584     5583       -1     
- Misses         980      984       +4     

Files Changed	Coverage Δ
src/bootstrap/app.rs	75.00% <ø> (+19.44%)	⬆️
src/bootstrap/config.rs	0.00% <0.00%> (ø)
packages/configuration/src/lib.rs	81.98% <16.66%> (+3.28%)	⬆️

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[josecelano]

There is a breaking change. I have removed the error when the default configuration is created:

Loading configuration from config file ./config.toml
thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: CreatedNewConfigHalt { location: Location { file: "packages/configuration/src/lib.rs", line: 520, col: 27 }, path: "./config.toml" }', src/bootstrap/app.rs:83:52
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Now the tracker continues running with the default configuration file:

Loading configuration from configuration file: `./config.toml` ...
Missing configuration file.
Creating a default configuration file: `./config.toml` ...
Please review the config file: `./config.toml` and restart the tracker if needed.
2023-08-08T12:16:24.548218890+01:00 [torrust_tracker::bootstrap::logging][INFO] logging initialized.
2023-08-08T12:16:24.548805484+01:00 [torrust_tracker::bootstrap::jobs::tracker_apis][INFO] Starting Torrust APIs server on: http://127.0.0.1:1212
2023-08-08T12:16:24.548882463+01:00 [torrust_tracker::bootstrap::jobs::tracker_apis][INFO] Torrust APIs server started

If we implement the issue to make the database optional and we make the no-database option the default one, we could run the tracker with default configuration (only memory) with a single docker command.

Alternatively, we could add a new env var TORRUST_TRACKER_USE_DEFAULT_CONFIG. If the env var is present, we do not even write the config file with the default config, we simply use the default config only in memory. What do you think @da2ce7?