Add batch update support to JdbcClient

[Empatixx]

This adds batch update support to JdbcClient, as requested in gh-33843.

Batch entries are accumulated in a fluent way through a new batch() method on StatementSpec:

int[] rowsAffected = client.sql("INSERT INTO user (first_name, last_name) VALUES (:first, :last)")
        .batch()
            .param("first", "Jane").param("last", "Smith").add()
            .param("first", "John").param("last", "Doe")
        .batchUpdate();

Each entry is bound with param(...) / params(...) / paramSource(...) exactly like a single update; add() separates entries and batchUpdate() executes them as one JDBC batch (the last entry is completed implicitly). Both positional and named parameters are supported (mixing the two in one batch is rejected). It delegates to JdbcOperations.batchUpdate / NamedParameterJdbcOperations.batchUpdate.

Reference docs and integration tests are included. The spring-jdbc build, Checkstyle and tests pass.

I know this is assigned to @sdeleuze — feel free to take whatever is useful here.

[quaff]

I'm expecting more fluent batch API like:

client.sql("insert into person(name, age) values (:name, :age)").batch().param("name", name1).param("age", age1).add().param("name", name2).param("age", age2).batchUpdate();

[Empatixx]

Updated the PR. Batch support is now a single fluent batch() API on StatementSpec: bind each entry with param(...) like a normal update, separate entries with add(), and run them with batchUpdate() (the final entry is flushed automatically). Works for both positional and named parameters. Reference docs and tests updated; the spring-jdbc build, Checkstyle and tests are green.

[quaff]

@Empatixx I added batch update with generated keys base on your commit, see https://github.com/quaff/spring-framework/tree/jdbcclient-batch-update

[sbrannen]

@Empatixx I added batch update with generated keys base on your commit, see quaff/spring-framework@jdbcclient-batch-update

@quaff, did you intend to submit a PR for that, or did I overlook an existing one?

[quaff]

@quaff, did you intend to submit a PR for that, or did I overlook an existing one?

@sbrannen, I created #37216 base on this PR.