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_meta_constraints/test_check_constraints.py

@@ -0,0 +1,57 @@
+import sqlite3
+
+import asyncpg  # type: ignore
+import databases
+import pytest
+import sqlalchemy
+
+import ormar.fields.constraints
+from tests.settings import DATABASE_URL
+
+database = databases.Database(DATABASE_URL, force_rollback=True)
+metadata = sqlalchemy.MetaData()
+
+
+class Product(ormar.Model):
+    class Meta:
+        tablename = "products"
+        metadata = metadata
+        database = database
+        constraints = [
+            ormar.fields.constraints.CheckColumns("inventory > buffer"),
+        ]
+
+    id: int = ormar.Integer(primary_key=True)
+    name: str = ormar.String(max_length=100)
+    company: str = ormar.String(max_length=200)
+    inventory: int = ormar.Integer()
+    buffer: int = ormar.Integer()
+
+
+@pytest.fixture(autouse=True, scope="module")
+def create_test_database():
+    engine = sqlalchemy.create_engine(DATABASE_URL)
+    metadata.drop_all(engine)
+    metadata.create_all(engine)
+    yield
+    metadata.drop_all(engine)
+
+
+@pytest.mark.asyncio
+async def test_check_columns_exclude_mysql():
+    if Product.Meta.database._backend._dialect.name != "mysql":
+        async with database:  # pragma: no cover
+            async with database.transaction(force_rollback=True):
+                await Product.objects.create(
+                    name="Mars", company="Nestle", inventory=100, buffer=10
+                )
+
+                with pytest.raises(
+                    (
+                        sqlite3.IntegrityError,
+                        asyncpg.exceptions.CheckViolationError,
+                    )
+                ):
+                    await Product.objects.create(
+                        name="Cookies", company="Nestle", inventory=1, buffer=10
+                    )