Move types related to list options and sql queries into their own package. (#610)

The problem having these in the informer package is that eventually code
in other packages will need to import `informer` only for constants or types,
but some members of the informer package may already depend on those. Best to
move type definitions into their own simpler package.

pkg/sqlcache/sqltypes/types.go

@@ -0,0 +1,78 @@
+package sqltypes
+
+type Op string
+
+const (
+	Eq        Op = "="
+	NotEq     Op = "!="
+	Exists    Op = "Exists"
+	NotExists Op = "NotExists"
+	In        Op = "In"
+	NotIn     Op = "NotIn"
+	Lt        Op = "Lt"
+	Gt        Op = "Gt"
+)
+
+// SortOrder represents whether the list should be ascending or descending.
+type SortOrder int
+
+const (
+	// ASC stands for ascending order.
+	ASC SortOrder = iota
+	// DESC stands for descending (reverse) order.
+	DESC
+)
+
+// ListOptions represents the query parameters that may be included in a list request.
+type ListOptions struct {
+	ChunkSize  int
+	Resume     string
+	Filters    []OrFilter
+	Sort       Sort
+	Pagination Pagination
+}
+
+// Filter represents a field to filter by.
+// A subfield in an object is represented in a request query using . notation, e.g. 'metadata.name'.
+// The subfield is internally represented as a slice, e.g. [metadata, name].
+// Complex subfields need to be expressed with square brackets, as in `metadata.labels[example.com/moose]`,
+// but are mapped to the string slice ["metadata", "labels", "example.com/moose"]
+//
+// If more than one value is given for the `Match` field, we do an "IN (<values>)" test
+type Filter struct {
+	Field   []string
+	Matches []string
+	Op      Op
+	Partial bool
+}
+
+// OrFilter represents a set of possible fields to filter by, where an item may match any filter in the set to be included in the result.
+type OrFilter struct {
+	Filters []Filter
+}
+
+// Sort represents the criteria to sort on.
+// The subfield to sort by is represented in a request query using . notation, e.g. 'metadata.name'.
+// The subfield is internally represented as a slice, e.g. [metadata, name].
+// The order is represented by prefixing the sort key by '-', e.g. sort=-metadata.name.
+// e.g. To sort internal clusters first followed by clusters in alpha order: sort=-spec.internal,spec.displayName
+type Sort struct {
+	Fields [][]string
+	Orders []SortOrder
+}
+
+type SortList struct {
+	SortDirectives []Sort
+}
+
+// Pagination represents how to return paginated results.
+type Pagination struct {
+	PageSize int
+	Page     int
+}
+
+func NewSortList() *SortList {
+	return &SortList{
+		SortDirectives: []Sort{},
+	}
+}