Support longer names for newer versions of Oracle

[weralabaj]

In versions 12.2 and above the max name length is 128 bytes (source), but we always assume the max length is 30 bytes (as in Oracle 12.1 and below).

[SzymonPobiega]

I see two ways we can handle this. Either make it configurable or have a separate dialect. The advantage of the latter is that we not only limit/validate the names but also have stuff like hash-based index names. With 128 chars we could get away without hashes altogether I guess.

[MarcinHoppe]

:+1: for a separate dialect like in NHibernate.

[DavidBoike]

Capturing what we discussed today:

• Separate dialect might be OK, but could double maintainability costs if most of the implementation of Oracle is duplicated. Perhaps the dialect only inherits and overrides a table name formatting function. But then it's not far off from a "don't throw if too long" option.
• Need to be cognizant of forward/backward compatibility. If switching dialects or enabling an option results in mass changes to lots of table names, then that's a compatibility challenge. May be preferable to have a "stop throwing" option that would leave all existing names alone but just stop complaining if new, longer-named endpoints (with no table prefix metadata) are created in the future.

[mikeminutillo]

Discussing it again today, we decided that the best approach is to make it configurable.