feat: Support skipping PK validation for columns (#2310)

#### Summary

So we don't have to insert empty values instead of nulls as a workaround (see cloudquery/cloudquery-private#9411)

Author: erezrokah

schema/column.go

@@ -49,6 +49,9 @@ type Column struct {
 
 	// If the column type is JSON, this field will have a JSON string that represents the schema of the JSON object.
 	TypeSchema string `json:"type_schema,omitempty"`
+
+	// Some PK columns can be nullable if there are a part of a composite PK, so we want to skip validation for them.
+	SkipPKValidation bool `json:"skip_pk_validation"`
 }
 
 // NewColumnFromArrowField creates a new Column from an arrow.Field

schema/resource.go

@@ -152,6 +152,9 @@ func (r *Resource) Validate() error {
 	var missingPks []string
 	var missingPKComponents []string
 	for i, c := range r.Table.Columns {
+		if c.SkipPKValidation {
+			continue
+		}
 		switch {
 		case c.PrimaryKey && !r.data[i].IsValid():
 			missingPks = append(missingPks, c.Name)

schema/resource_test.go

@@ -45,6 +45,21 @@ func TestResource_Validate(t *testing.T) {
 			resource: NewResourceData(&Table{Name: "test", Columns: ColumnList{{Name: "col1", Type: arrow.BinaryTypes.String, PrimaryKeyComponent: true}}}, nil, nil),
 			err:      &PKComponentError{MissingPKComponents: []string{"col1"}},
 		},
+		{
+			name: "valid resource with primary key components and skip validation",
+			resource: NewResourceData(&Table{Name: "test", Columns: ColumnList{
+				{
+					Name: "col1", Type: arrow.BinaryTypes.String, PrimaryKeyComponent: true,
+				},
+				{
+					Name: "col2", Type: arrow.BinaryTypes.String, PrimaryKey: true, SkipPKValidation: true,
+				},
+			}}, nil, nil),
+			err: nil,
+			valueSetter: func(resource *Resource) error {
+				return resource.Set("col1", "test")
+			},
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {