Fix modification of SQL Server column type

- Fix modification of SQL Server column type
- Few refactor around using QuotedName
- Add unit test change_column_type_sql

src/Weasel.SqlServer.Tests/Tables/TableColumnTests.cs

@@ -118,4 +118,17 @@ public void add_column_sql()
         column.AddColumnSql(table)
             .ShouldBe("alter table dbo.people add name1 varchar(100) NOT NULL;");
     }
+
+    [Fact]
+    public void change_column_type_sql()
+    {
+        var table = new Table("people");
+        const string columnName = "order";
+        table.AddColumn<string>(columnName).NotNull();
+
+        var updatedColumn = new TableColumn(columnName, "varchar(200)") { AllowNulls = true };
+
+        table.ColumnFor("order")!.AlterColumnTypeSql(table, updatedColumn)
+            .ShouldBe($"alter table dbo.people alter column [{columnName}] varchar(200) NULL;");
+    }
 }

src/Weasel.SqlServer/Tables/TableColumn.cs

@@ -66,7 +66,7 @@ public string Declaration()
 
     protected bool Equals(TableColumn other)
     {
-        return string.Equals(Name, other.Name) &&
+        return string.Equals(QuotedName, other.QuotedName) &&
                string.Equals(SqlServerProvider.Instance.ConvertSynonyms(RawType()),
                    SqlServerProvider.Instance.ConvertSynonyms(other.RawType()));
     }
@@ -116,12 +116,12 @@ public override string ToString()
 
     public virtual string AlterColumnTypeSql(Table table, TableColumn changeActual)
     {
-        return $"alter table {table.Identifier} modify column {Name.PadRight(Name.Length)} type {Type};";
+        return $"alter table {table.Identifier} alter column {changeActual.ToDeclaration()};";
     }
 
     public string DropColumnSql(Table table)
     {
-        return $"alter table {table.Identifier} drop column {Name};";
+        return $"alter table {table.Identifier} drop column {QuotedName};";
     }