fix: set byte length for operation.logs column

[SteBaum]

Which issue(s) this PR fixes

Fixes None

Additional comments

Deployment on MariaDB fails if no byte length is set for the column logs in table operation. The length has been set at 10 000 000. It has been tested with 1 000 000 and it worked. The maximum length in a deployment is grafana_server_config | 611501.

In PR #590 a test is included which adds text in the logs column to see if passes on every database.

Agreements

• [x] I hereby declare this contribution to be licensed under the Apache License Version 2.0, January 2004.
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