CheckColumns Constraint (#730)

* feat: add check columns class

* feat: write document of check columns part

* test: write a test for check columns constraints

* fix: debuging test exception raise mysql

* fix: set pragma no cover to ignore cov

* fix: ignore pytest raise in python 3.x not 10

* feat: set constraint name for check columns

* refactor: support index and check overwrites

* fix: debuging check constraint arguments

* fix: debug coverage all code tests

* fix: pass the map of type constraint to counter

* refactor: edit check name replace sapce underline

* refactor: write new function copy constraints

* test: write test for invalid constraint type

* fix: debug text cluase replaced names

* fix: set pragma no cover for result returned

* refactor: no coverage for main if statement

* perf: change get constraint copy func code

* fix: fix bug in mypy typing check

tests/test_inheritance_and_pydantic_generation/test_inheritance_concrete.py

@@ -1,6 +1,7 @@
 # type: ignore
 import datetime
 from typing import List, Optional
+from collections import Counter
 
 import databases
 import pytest
@@ -11,6 +12,7 @@ import ormar
 import ormar.fields.constraints
 from ormar import ModelDefinitionError, property_field
 from ormar.exceptions import ModelError
+from ormar.models.metaclass import get_constraint_copy
 from tests.settings import DATABASE_URL
 
 metadata = sa.MetaData()
@@ -47,7 +49,13 @@ class DateFieldsModel(ormar.Model):
         metadata = metadata
         database = db
         constraints = [
-            ormar.fields.constraints.UniqueColumns("creation_date", "modification_date")
+            ormar.fields.constraints.UniqueColumns(
+                "creation_date",
+                "modification_date",
+            ),
+            ormar.fields.constraints.CheckColumns(
+                "creation_date <= modification_date",
+            ),
         ]
 
     created_date: datetime.datetime = ormar.DateTime(
@@ -234,9 +242,13 @@ def test_model_subclassing_non_abstract_raises_error():
 def test_params_are_inherited():
     assert Category.Meta.metadata == metadata
     assert Category.Meta.database == db
-    assert len(Category.Meta.constraints) == 2
     assert len(Category.Meta.property_fields) == 2
 
+    constraints = Counter(map(lambda c: type(c), Category.Meta.constraints))
+    assert constraints[ormar.fields.constraints.UniqueColumns] == 2
+    assert constraints[ormar.fields.constraints.IndexColumns] == 0
+    assert constraints[ormar.fields.constraints.CheckColumns] == 1
+
 
 def round_date_to_seconds(
     date: datetime.datetime,
@@ -519,3 +531,8 @@ def test_custom_config():
     sam = ImmutablePerson(name="Sam")
     with pytest.raises(TypeError):
         sam.name = "Not Sam"
+
+
+def test_get_constraint_copy():
+    with pytest.raises(ValueError):
+        get_constraint_copy("INVALID CONSTRAINT")