R2DBC @Sequence annotation support

[mipo256]

Hey @mp911de! As discussed here, I've provided the corresponding PR for the Spring Data R2DBC module for @Sequence support.

I've also provided the adoc documentation for this feature, I think it is worth a separate small page. I can do the same for the Spring Data JDBC module, should I? @mp911de

[mp911de]

Thanks a lot. Let me check how the documentation fits into both modules. Maybe we can have a shared fragment for inclusion.

[mp911de]

Obtaining the IdColumn as early as possible guards the later code against potential absence. Also, there's repetative access to IdProperty. I think it would be much more aligned with a future support of embedded Id's to use the IdProperty instead of IdColumn.

[mipo256]

I think it would be much more aligned with a future support of embedded Id's to use the IdProperty instead of IdColumn.

Can you please elaborate on what you mean here? The OutboundRow contains the mapping between column names (not properties) and their repsective values. I can obtain the idProperty once (although, this operation is relatively cheap since it just returns a reference to an already computed Id PersistentProperty), but I do not see how we can use the property here intead of column.

[mp911de]

This is a difference between persistentEntity.getIdColumn() and PersistentProperty.getColumnName().

[mipo256]

I still do not understand what change needs to be done here to be honest @mp911de

This is a difference between persistentEntity.getIdColumn() and PersistentProperty.getColumnName().

The persistentEntity.getIdColumn() is implemeted internally as getRequiredIdProperty().getColumnName(), which partically the same as calling the PersistentProperty.getColumnName().