Additional contextual information intended for end users, to help them
understand what went wrong by providing human-readable messages, and
locations in the source query that relate to the error in some way.
A “help” enriches a Diagnostic with extra information, possibly
referring to different locations in the original SQL query, that helps the
user understand how they might fix the error or warning.
A note enriches a Diagnostic with extra information, possibly referring
to different locations in the original SQL query, that helps contextualize
the error and helps the end user understand why it occurred.
A Diagnostic can either be a hard error that prevents the query from
being planned and executed, or a warning that indicates potential issues,
performance problems, or causes for unexpected results, but is non-fatal.
This enum expresses these two possibilities.