v0.20.0rc1 (release cut 1)

cutting a release for last minute testing and to make it easier to bring dbt-synapse to

features:

• dbt-sqlserver will now work with dbt v0.20.0. Please see dbt's upgrading to v0.20.0 docs for more info.
• users can now declare a custom max_batch_size in the project configuration to set the batch size used by the seed file loader. #127 and #151 thanks @jacobm001

under the hood

• sqlserver__load_csv_rows now has a safety provided by calc_batch_size() to ensure the insert statements won't exceed SQL Server's 2100 parameter limit. #127 and #151 thanks @jacobm001
• switched to using a MANIFEST.in to declare which files should be included
• updated pyodbc and azure-identity dependencies to their latest versions