Move the libs/pubsub package to internal scope (#7451)

No API changes, merely changes the import path.

internal/pubsub/query/syntax/doc.go

@@ -0,0 +1,34 @@
+// Package syntax defines a scanner and parser for the Tendermint event filter
+// query language. A query selects events by their types and attribute values.
+//
+// Grammar
+//
+// The grammar of the query language is defined by the following EBNF:
+//
+//   query      = conditions EOF
+//   conditions = condition {"AND" condition}
+//   condition  = tag comparison
+//   comparison = equal / order / contains / "EXISTS"
+//   equal      = "=" (date / number / time / value)
+//   order      = cmp (date / number / time)
+//   contains   = "CONTAINS" value
+//   cmp        = "<" / "<=" / ">" / ">="
+//
+// The lexical terms are defined here using RE2 regular expression notation:
+//
+//   // The name of an event attribute (type.value)
+//   tag    = #'\w+(\.\w+)*'
+//
+//   // A datestamp (YYYY-MM-DD)
+//   date   = #'DATE \d{4}-\d{2}-\d{2}'
+//
+//   // A number with optional fractional parts (0, 10, 3.25)
+//   number = #'\d+(\.\d+)?'
+//
+//   // An RFC3339 timestamp (2021-11-23T22:04:19-09:00)
+//   time   = #'TIME \d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}([-+]\d{2}:\d{2}|Z)'
+//
+//   // A quoted literal string value ('a b c')
+//   value  = #'\'[^\']*\''
+//
+package syntax