[lehni]

Follow-up for #429 before 4.3.0: strict graphs get explicit defaults and exact comparisons. Strict mode is unreleased, so this changes its semantics without breaking anything that was released.

• added: 'throw' is now a value and the default of upsertGraph(), for relations and root. It names what an unset added did before (the NotFoundError with its hints), and a later entry can now narrow an earlier '*': { added: 'relate' } for one relation. insertGraph() keeps the default 'insert' and accepts 'throw' to stop inserting rows with ids.
• removed has no default. Every relation that a strict graph contains, at any depth and also when given as null or [], needs a removed setting from some entry. Otherwise the call throws a ValidationError of type InvalidGraph that lists the relations, before anything is loaded or written. Relations inside rows marked #delete or #unrelate are exempt, since they're ignored.
• Rows given only by the key of a BelongsToOneRelation are always added rows. The special case that let created decide when added wasn't set is gone.
• Comparisons are exact. kept: 'preserve' and the strict placement checks no longer use ==, so '', ' ' and false don't equal 0. Numbers match numeric strings ('1.50' and 1.5), booleans match 1/0, dates compare by time, Buffers by bytes and bigints exactly.
• The docs and typings show the default of each setting next to its values.