Enforce for max_lifetime in pool.check()

[dvarrazzo]

I'm also thinking that check() might be a good moment to check if max_lifetime is expired, because it's already in the business of taking out all the connections from the pool and exercise them. This is much simpler and can be done in a bugfix for psycopg_pool 3.1. It would be up to the user to call pool.check() periodically.

Originally posted by @dvarrazzo in #247 (comment)

[dvarrazzo]

It should be as easy as (untested):

diff --git a/psycopg_pool/psycopg_pool/pool.py b/psycopg_pool/psycopg_pool/pool.py
index 609d95df..47c9561b 100644
--- a/psycopg_pool/psycopg_pool/pool.py
+++ b/psycopg_pool/psycopg_pool/pool.py
@@ -409,6 +409,13 @@ class ConnectionPool(BasePool[Connection[Any]]):
 
         while conns:
             conn = conns.pop()
+
+            if conn._expire_at <= monotonic():
+                logger.info("discarding expired connection %s", conn)
+                conn.close()
+                self.run_task(AddConnection(self))
+                continue
+
             try:
                 conn.execute("SELECT 1")
                 if conn.pgconn.transaction_status == TransactionStatus.INTRANS:

It needs the equivalent async, tests in the test suite, an entry in the changelog.

It seems simple enough if someone would like to try it.