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

docs/api/models/model-metaclass.md

@@ -12,61 +12,6 @@ Class used for type hinting.
 Users can subclass this one for convenience but it's not required.
 The only requirement is that ormar.Model has to have inner class with name Meta.
 
-<a name="models.metaclass.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.metaclass.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.metaclass.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
-
 <a name="models.metaclass.add_cached_properties"></a>
 #### add\_cached\_properties
 
@@ -87,26 +32,6 @@ All properties here are used as "cache" to not recalculate them constantly.
 
 - `new_model (Model class)`: newly constructed Model
 
-<a name="models.metaclass.meta_field_not_set"></a>
-#### meta\_field\_not\_set
-
-```python
-meta_field_not_set(model: Type["Model"], field_name: str) -> bool
-```
-
-Checks if field with given name is already present in model.Meta.
-Then check if it's set to something truthful
-(in practice meaning not None, as it's non or ormar Field only).
-
-**Arguments**:
-
-- `model (Model class)`: newly constructed model
-- `field_name (str)`: name of the ormar field
-
-**Returns**:
-
-`(bool)`: result of the check
-
 <a name="models.metaclass.add_property_fields"></a>
 #### add\_property\_fields
 
@@ -141,24 +66,6 @@ Signals are emitted in both model own methods and in selected queryset ones.
 
 - `new_model (Model class)`: newly constructed model
 
-<a name="models.metaclass.update_attrs_and_fields"></a>
-#### update\_attrs\_and\_fields
-
-```python
-update_attrs_and_fields(attrs: Dict, new_attrs: Dict, model_fields: Dict, new_model_fields: Dict, new_fields: Set) -> Dict
-```
-
-Updates __annotations__, values of model fields (so pydantic FieldInfos)
-as well as model.Meta.model_fields definitions from parents.
-
-**Arguments**:
-
-- `attrs (Dict)`: new namespace for class being constructed
-- `new_attrs (Dict)`: related of the namespace extracted from parent class
-- `model_fields (Dict[str, BaseField])`: ormar fields in defined in current class
-- `new_model_fields (Dict[str, BaseField])`: ormar fields defined in parent classes
-- `new_fields (Set[str])`: set of new fields names
-
 <a name="models.metaclass.verify_constraint_names"></a>
 #### verify\_constraint\_names
 
@@ -195,7 +102,7 @@ Updates Meta parameters in child from parent if needed.
 #### copy\_and\_replace\_m2m\_through\_model
 
 ```python
-copy_and_replace_m2m_through_model(field: Type[ManyToManyField], field_name: str, table_name: str, parent_fields: Dict, attrs: Dict, meta: ModelMeta) -> None
+copy_and_replace_m2m_through_model(field: Type[ManyToManyField], field_name: str, table_name: str, parent_fields: Dict, attrs: Dict, meta: ModelMeta, base_class: Type["Model"]) -> None
 ```
 
 Clones class with Through model for m2m relations, appends child name to the name
@@ -211,6 +118,7 @@ Removes the original sqlalchemy table from metadata if it was not removed.
 
 **Arguments**:
 
+- `base_class (Type["Model"])`: base class model
 - `field (Type[ManyToManyField])`: field with relations definition
 - `field_name (str)`: name of the relation field
 - `table_name (str)`: name of the table
@@ -281,6 +189,24 @@ If the class is a ormar.Model it is skipped.
 
 `(Tuple[Dict, Dict])`: updated attrs and model_fields
 
+<a name="models.metaclass.update_attrs_and_fields"></a>
+#### update\_attrs\_and\_fields
+
+```python
+update_attrs_and_fields(attrs: Dict, new_attrs: Dict, model_fields: Dict, new_model_fields: Dict, new_fields: Set) -> Dict
+```
+
+Updates __annotations__, values of model fields (so pydantic FieldInfos)
+as well as model.Meta.model_fields definitions from parents.
+
+**Arguments**:
+
+- `attrs (Dict)`: new namespace for class being constructed
+- `new_attrs (Dict)`: related of the namespace extracted from parent class
+- `model_fields (Dict[str, BaseField])`: ormar fields in defined in current class
+- `new_model_fields (Dict[str, BaseField])`: ormar fields defined in parent classes
+- `new_fields (Set[str])`: set of new fields names
+
 <a name="models.metaclass.ModelMetaclass"></a>
 ## ModelMetaclass Objects