ADR 015: home db caching

[robsdedude]

Add max_home_database_delay config option to the driver. Defines an upper bound for how long (in seconds) a resolved home database can be cached. It defaults to 5.0 seconds.

This should improve performance by reducing the extra round trips needed for resolving the home database. However, this also means that home database changes might become visible later in the driver than they used to. There are different options how to tackle this, should this be a problem.

1. Reduce the value of max_home_database_delay. This can go as far to to set it to 0 effectively restoring the driver's behavior before this change. However, extrem values are likely to incur a significant performance penalty (driver and server side).
2. Call the new driver.force_home_database_resolution() to make the driver forget any cached home dbs. This is especially useful after a home database change has been issued and needs to be readable from the same application directly afterwards.

Depends on

• https://github.com/neo4j-drivers/testkit/pull/569

Should be ported back to 4.4

[robsdedude]

ADR has been abandoned because the change was considered too risky. Better approaches are being discussed.