[DO NOT MERGE] POC of propagation for sql server via SET CONTEXT_INFO

[XSAM]

This PR a prototype to demonstrate how SET CONTEXT_INFO can be used in the real world.

https://github.com/XSAM/otelsql/pull/508/files#diff-4f427d2b022907c552328e63f137561f6de92396d7a6e8f6c2ea1bcf0db52654R291 is the change for otelsql to make this happen.

Steps to run the example:

• Go to example/sqlserver folder
• docker compose up -d This runs a sql server, otel collector, jaeger and sql client.
• docker compose up client to run a query from sql client. Meanwhile,
• run this query against sql server database to fetch query samples

SELECT Substring(o.text, ( r.statement_start_offset / 2 ) + 1,
                 ( ( CASE r.statement_end_offset
                         WHEN -1 THEN Datalength(o.text)
                         ELSE r.statement_end_offset
                         END -
                     r.statement_start_offset ) / 2 ) + 1)          AS statement_text,
       o.text                                         AS text,
       Isnull(r.context_info, CONVERT(VARBINARY, '')) AS context_info
FROM   sys.dm_exec_requests r
           INNER JOIN sys.dm_exec_sessions s
                      ON r.session_id = s.session_id
           INNER JOIN sys.dm_exec_connections c
                      ON s.session_id = c.session_id
           CROSS apply sys.dm_exec_sql_text(r.plan_handle) AS o

Example results:

statement_text	text	context_info
WAITFOR DELAY '00:00:05'	SELECT * FROM sys.dm_exec_connections; WAITFOR DELAY '00:00:05'	00-13df7cc8a541ad6de8b0d347e7618625-b0e43abf9390a766-01

From Jaeger

You will see the trace_id and trace_id from CONTEXT_INFO is linked to an existing span on Jaeger.