`splunksql`: Add `splunksql.OpenDB` function

[pellared]

Add splunksql.OpenDB function for ones who dislike the sql.Open and splunksql.Open which use global state.

Something similar to https://pkg.go.dev/github.com/XSAM/otelsql#OpenDB

Desired API: func OpenDB(c driver.Connector, cfg InstrumentationConfig) *sql.DB.
We should also add OpenDB functions to all other sql-based instrumentation libraries that will use splunksql.OpenDB.

Implementation guidelines: #88 (comment)

Originally posted by @pellared in #88 (comment)

[pellared]

Waiting until anyone asks for this feature.

[ccoqueiro]

Is it possible to use this feature for dynamodb or s3 calls?

[pellared]

@ccoqueiro Can you be more precise in your question? If you ask about AWS DynamoDB and S3 instrumentation then it should be possible using the otelaws instrumentation library (here you can find also some AWS docs and here is an example usage)

Hi, we want splunksql.OpenDB function. We want to use pgx Connector's option (e.g. OptionAfterConnect) but we can't use it with splunksql.

[pellared]

@joshi-kamitsukasa Could you please add a snippet how would you use such function?

My guess is that it would rather prefer using func OpenDB(config pgx.ConnConfig, opts ...stdlib.OptionOpenDB) *sql.DB that could be added to https://pkg.go.dev/github.com/signalfx/splunk-otel-go/instrumentation/github.com/jackc/pgx/v5/splunkpgx.

Of course we would need to create splunksql.OpenDB anyway 😉

If you would like to have this sooner rather than later, please contact Splunk's support/sales to escalate this issue. More: https://docs.splunk.com/observability/en/get-started/support.html

@pellared Thanks for your reply.

For example below,

	return stdlib.OpenDB(*pgxConfig, []stdlib.OptionOpenDB{
		stdlib.OptionAfterConnect(func(ctx context.Context, conn *pgx.Conn) error {
			pgxdecimal.Register(conn.TypeMap())
			return setXxxxxFunc(ctx, conn)
		}),
		stdlib.OptionResetSession(setXxxxxFunc),
	}...), nil

We are going to contact support. Thanks.