sql: introduce and mandate explicit PostgreSQL connections

[benesch]

Introduce a new PostgreSQL connection type, as in...

CREATE CONNECTION pgconn FOR POSTGRES
  HOST postgres,
  DATABASE postgres,
  USER postgres,
  PASSWORD SECRET pgpass;

CREATE SOURCE pg FOR POSTGRES CONNECTION pgconn;

The connection options correspond to the old libpq connection parameters
in the obvious way.

As decided in https://github.com/MaterializeInc/database-issues/issues/3838, this commit also removes the old syntax for
specifying PostgreSQL connection details inline in the CREATE SOURCE
statement; connection details must now be specified in CREATE CONNECTION.

Touches https://github.com/MaterializeInc/database-issues/issues/3354.
Touches https://github.com/MaterializeInc/database-issues/issues/3838.

Motivation

• This PR adds a known-desirable feature.

Testing

• This PR has adequate test coverage / QA involvement has been duly considered.

Release notes

This PR includes the following user-facing behavior changes:

• See description.

[sploiselle]

Think this was meant to be a passing test

[benesch]

D'oh! Thanks.

[benesch]

This is fixed!

[sploiselle]

Oh, derp--this shouldn't be necessary! Looks like we missed adding this diff:

diff --git a/src/testdrive/src/action/sql.rs b/src/testdrive/src/action/sql.rs
index b9b58f807..1e129c2c7 100644
--- a/src/testdrive/src/action/sql.rs
+++ b/src/testdrive/src/action/sql.rs
@@ -27,9 +27,9 @@ use mz_ore::retry::Retry;
 use mz_ore::str::StrExt;
 use mz_pgrepr::{Interval, Jsonb, Numeric};
 use mz_sql_parser::ast::{
-    CreateClusterReplicaStatement, CreateClusterStatement, CreateDatabaseStatement,
-    CreateSchemaStatement, CreateSecretStatement, CreateSourceStatement, CreateTableStatement,
-    CreateViewStatement, Raw, ReplicaDefinition, Statement, ViewDefinition,
+    CreateClusterReplicaStatement, CreateClusterStatement, CreateConnectionStatement,
+    CreateDatabaseStatement, CreateSchemaStatement, CreateSecretStatement, CreateSourceStatement,
+    CreateTableStatement, CreateViewStatement, Raw, ReplicaDefinition, Statement, ViewDefinition,
 };
 
 use crate::action::{Action, ControlFlow, State};
@@ -140,6 +140,13 @@ impl Action for SqlAction {
                 )
                 .await
             }
+            Statement::CreateConnection(CreateConnectionStatement { name, .. }) => {
+                self.try_drop(
+                    &mut state.pgclient,
+                    &format!("DROP CONNECTION IF EXISTS {} CASCADE", name),
+                )
+                .await
+            }
             _ => Ok(()),
         }

Line above should already be unnecessary.

[benesch]

Ah, you're totally right that this was missed, but also this testdrive script runs with --no-reset so the logic there doesn't apply. So I applied your patch and left the code in question in place!

[sploiselle]

ah til

[benesch]

Thanks very much for the thorough review, @sploiselle!