`ColumnTypes` is not JSON serializable

[basteks]

While trying to use a member of the ColumnTypes class in a dict object, we get a TypeError: Object of type ColumnTypes is not JSON serializable.

This is quite counterintuitive as most of the columns functions require a ColumnTypes member instead of a simple string such as 'text' or 'number', whereas you can't provide such a member in an API request such as:

import requests
from seatable_api import Base, context
from seatable_api.constants import ColumnTypes

base = Base(context.api_token, context.server_url)
base.auth()

url = f"https://cloud.seatable.io/api-gateway/api/v2/dtables/{base.dtable_uuid}/columns"

payload = {
    "op_type": "modify_column_type",
    "column_data": {
        "table": "Table1",
        "other_table": "Table2"
    },
    "table_name": "Table1",
    "column": "aa",
    "new_column_type": ColumnTypes.IMAGE # for now, you have to write 'image'
}

headers = {
    "accept": "application/json",
    "content-type": "application/json",
    "authorization": f"Bearer {base.jwt_token}"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)