dialect/entsql: supports setting SQL column comments (#3191)

* feat: Add column comment in SQL DDL, using EntSQL annotations to achieve it.

* Update annotation.go

* fix lint

* Add table primary key column comment

* entsql.Comment(string)  is unnecessary

* entc/gen: minor changes to entsql.WithComments + add tests

Co-authored-by: chenghonour <wantto@outlook.com>

dialect/sql/schema/atlas.go

@@ -912,6 +912,9 @@ func (a *Atlas) aColumns(et *Table, at *schema.Table) error {
 		if c1.Collation != "" {
 			c2.SetCollation(c1.Collation)
 		}
+		if c1.Comment != "" {
+			c2.SetComment(c1.Comment)
+		}
 		if err := a.sqlDialect.atTypeC(c1, c2); err != nil {
 			return err
 		}

dialect/sql/schema/schema.go

@@ -295,6 +295,7 @@ type Column struct {
 	typ        string            // row column type (used for Rows.Scan).
 	indexes    Indexes           // linked indexes.
 	foreign    *ForeignKey       // linked foreign-key.
+	Comment    string            // column comment.
 }
 
 // Expr represents a raw expression. It is used to distinguish between