feat: Add MySQL sample data loader

[madison-ookla]

Summary of Changes

This PR adds a MySQL sample data loader similar to the sample Postgres loader (almost everything is the same from that loader save the metadata extractor and the config settings).

Here's the diff between files:

File Diff

17c17
< from databuilder.extractor.postgres_metadata_extractor import PostgresMetadataExtractor
---
> from databuilder.extractor.mysql_metadata_extractor import MysqlMetadataExtractor
57,59c57,59
<     port = '5432'
<     db = 'postgres'
<     return "postgresql://%s@%s:%s/%s" % (user, host, port, db)
---
>     port = '3306'
>     db = 'mysql'
>     return "mysql://%s@%s:%s/%s" % (user, host, port, db)
62c62
< def run_postgres_job():
---
> def run_mysql_job():
64c64
<         where table_schema = 'public'
---
>         where c.table_schema = 'mysql'
72c72
<         'extractor.postgres_metadata.{}'.format(PostgresMetadataExtractor.WHERE_CLAUSE_SUFFIX_KEY):
---
>         'extractor.mysql_metadata.{}'.format(MysqlMetadataExtractor.WHERE_CLAUSE_SUFFIX_KEY):
74c74
<         'extractor.postgres_metadata.{}'.format(PostgresMetadataExtractor.USE_CATALOG_AS_CLUSTER_NAME):
---
>         'extractor.mysql_metadata.{}'.format(MysqlMetadataExtractor.USE_CATALOG_AS_CLUSTER_NAME):
76c76
<         'extractor.postgres_metadata.extractor.sqlalchemy.{}'.format(SQLAlchemyExtractor.CONN_STRING):
---
>         'extractor.mysql_metadata.extractor.sqlalchemy.{}'.format(SQLAlchemyExtractor.CONN_STRING):
96c96
<                      task=DefaultTask(extractor=PostgresMetadataExtractor(), loader=FsNeo4jCSVLoader()),
---
>                      task=DefaultTask(extractor=MysqlMetadataExtractor(), loader=FsNeo4jCSVLoader()),
168c168
<     loading_job = run_postgres_job()
---
>     loading_job = run_mysql_job()

Tests

As far as I can tell, there aren't any tests for the example scripts.

Documentation

Most documentation is retained from the Postgres sample loader.

CheckList

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• PR passes make test

[feng-tao]

thanks @madison-ookla