fix instance types of log group fields

[markdboyd]

Changes proposed in this pull request:

• fix instance types of log group fields on instance structs so that they are actually saved to the database

Things to check

• For any logging statements, is there any chance that they could be logging sensitive data?
• Are log statements using a logging library with a logging level set? Setting a logging level means that log statements "below" that level will not be written to the output. For example, if the logging level is set to INFO and debugging statements are written with log.debug or similar, then they won't be written to the otput, which can prevent unintentional leaks of sensitive data.

Security considerations

None, just making sure that fields get written to the database rather than ignored