feat: Add logging feature for custom validators

docs/logging.md

@@ -0,0 +1,29 @@
+## Few words about logging
+
+There is a total of 4 logger included in the Phaistos package:
+
+<!-- TRANSPILATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (T)')
+MANAGER_LOGGER = phaistos.utils.setup_logger('PHAISTOS (M)')
+COMPILATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (C)')
+VALIDATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (V)') -->
+
+1. **PHAISTOS (T)**: This logger is used by the `Transpiler` class to log messages related to the transpilation process.
+2. **PHAISTOS (M)**: This logger is used by the `Manager` class to log messages related to the schema management.
+3. **PHAISTOS (C)**: This logger is used by the `Compiler` class to log messages related to the compilation process.
+4. **PHAISTOS (V)**: This logger is used by the `Manager` class to log messages related to the validation process i.e. things that happen **inside** custom validators.
+
+The logging level for all the loggers is set to `INFO` by default.
+
+Do You want to create a custom logger for Phaistos? You can do it by using the `phaistos.utils.setup_logger` function:
+
+```python
+from phaistos import utils
+
+logger = utils.setup_logger('MyLogger', level='DEBUG')
+```
+
+This will create a logger named `MyLogger` with the logging level set to `DEBUG`. You can use this logger to log messages in your custom code.
+
+**phaistos.utils.setup_logger**
+
+::: phaistos.utils.setup_logger

docs/main-features.md

@@ -77,9 +77,10 @@ classes in Python (which is a whole different can of worms), we can
 quickly install Phaistos in the project and start using it to validate
 data against the defined schemas - which can be leveraged in distributed ETL pipelines (e.g. within Apache Spark workers), APIs, configurations, and more.
 
-#### Minor nitpicks 🤏
+#### Minor nitpicks 🤏 and quality-of-life boons
 
-Below is the section that lists little annoyances that Phaistos tries to solve:
+Below is the section that lists little annoyances that Phaistos tries to solve
+or things that may be considered as quality-of-life improvements.
 
 1. Normally, Pydantic will **not run** field validators for any attributes
 that were used in the previously failed model validator. So, this is slightly
@@ -91,3 +92,6 @@ abstract names, Phaistos allows you to reference them by their actual
 names. So, in the custom validator, you can use `name` instead of `value`
 for a field that is named ... `name`! This makes the code more readable
 and maintainable.
+3. You can use logging via the `logger` variable inside **all** custom
+validators, which hooks up into the global validation logger. It is
+included by default in the transpiled code.

mkdocs.yml

@@ -24,6 +24,8 @@ nav:
   - Managing schemas:
     - Using validation mechanisms: manager.md
     - Skipping the autodiscovery: noauto.md
+  - Other features:
+    - Logging: logging.md
 markdown_extensions:
   - pymdownx.superfences:
       custom_fences:

phaistos/consts.py

@@ -6,6 +6,7 @@
 TRANSPILATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (T)')
 MANAGER_LOGGER = phaistos.utils.setup_logger('PHAISTOS (M)')
 COMPILATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (C)')
+VALIDATION_LOGGER = phaistos.utils.setup_logger('PHAISTOS (V)')
 
 ALLOWED_COLLECTION_TYPES = {'list', 'set'}