take pydantic's alias into account when serializing AvroBaseModel

[RuiLoureiro]

Describe the bug

I have an AvroBaseModel with a field named schema.
Because schema is already a method defined in pydantic's BaseModel I have to use an alias.

I am trying to serialize this model using https://github.com/marcosschroh/python-schema-registry-client.

The issue is that AvroBaseModel.asdict() ignores the alias

To Reproduce

from dataclasses_avroschema.pydantic import AvroBaseModel
from pydantic import Field

class Foo(AvroBaseModel):
    schema_: str = Field(alias='schema')

foo = Foo(schema='bar')

# raises error
assert 'schema' in foo.asdict()

Expected behavior

I would expect that when an AvroBaseModel is serialized, it would use the alias of each field (in this case, schema instead of schema_)