update docs, add load_all(), tests for load_all, make through field optional

docs/api/models/helpers/validation.md

@@ -0,0 +1,120 @@
+<a name="models.helpers.validation"></a>
+# models.helpers.validation
+
+<a name="models.helpers.validation.check_if_field_has_choices"></a>
+#### check\_if\_field\_has\_choices
+
+```python
+check_if_field_has_choices(field: Type[BaseField]) -> bool
+```
+
+Checks if given field has choices populated.
+A if it has one, a validator for this field needs to be attached.
+
+**Arguments**:
+
+- `field (BaseField)`: ormar field to check
+
+**Returns**:
+
+`(bool)`: result of the check
+
+<a name="models.helpers.validation.convert_choices_if_needed"></a>
+#### convert\_choices\_if\_needed
+
+```python
+convert_choices_if_needed(field: Type["BaseField"], value: Any) -> Tuple[Any, List]
+```
+
+Converts dates to isoformat as fastapi can check this condition in routes
+and the fields are not yet parsed.
+
+Converts enums to list of it's values.
+
+Converts uuids to strings.
+
+Converts decimal to float with given scale.
+
+**Arguments**:
+
+- `field (Type[BaseField])`: ormar field to check with choices
+- `values (Dict)`: current values of the model to verify
+
+**Returns**:
+
+`(Tuple[Any, List])`: value, choices list
+
+<a name="models.helpers.validation.validate_choices"></a>
+#### validate\_choices
+
+```python
+validate_choices(field: Type["BaseField"], value: Any) -> None
+```
+
+Validates if given value is in provided choices.
+
+**Raises**:
+
+- `ValueError`: If value is not in choices.
+
+**Arguments**:
+
+- `field (Type[BaseField])`: field to validate
+- `value (Any)`: value of the field
+
+<a name="models.helpers.validation.choices_validator"></a>
+#### choices\_validator
+
+```python
+choices_validator(cls: Type["Model"], values: Dict[str, Any]) -> Dict[str, Any]
+```
+
+Validator that is attached to pydantic model pre root validators.
+Validator checks if field value is in field.choices list.
+
+**Raises**:
+
+- `ValueError`: if field value is outside of allowed choices.
+
+**Arguments**:
+
+- `cls (Model class)`: constructed class
+- `values (Dict[str, Any])`: dictionary of field values (pydantic side)
+
+**Returns**:
+
+`(Dict[str, Any])`: values if pass validation, otherwise exception is raised
+
+<a name="models.helpers.validation.construct_modify_schema_function"></a>
+#### construct\_modify\_schema\_function
+
+```python
+construct_modify_schema_function(fields_with_choices: List) -> SchemaExtraCallable
+```
+
+Modifies the schema to include fields with choices validator.
+Those fields will be displayed in schema as Enum types with available choices
+values listed next to them.
+
+**Arguments**:
+
+- `fields_with_choices (List)`: list of fields with choices validation
+
+**Returns**:
+
+`(Callable)`: callable that will be run by pydantic to modify the schema
+
+<a name="models.helpers.validation.populate_choices_validators"></a>
+#### populate\_choices\_validators
+
+```python
+populate_choices_validators(model: Type["Model"]) -> None
+```
+
+Checks if Model has any fields with choices set.
+If yes it adds choices validation into pre root validators.
+
+**Arguments**:
+
+- `model (Model class)`: newly constructed Model
+