fix(postgrest): escape reserved characters in array filter values

[AndroidPoet]

What

Array's PostgrestFilterValue conformance builds a PostgreSQL array literal by joining the elements' raw values with commas, with no escaping:

extension Array: PostgrestFilterValue where Element: PostgrestFilterValue {
  public var rawValue: String {
    "{\(map(\.rawValue).joined(separator: ","))}"
  }
}

So any element that contains a character with structural meaning inside an array literal is silently corrupted. For example, filtering an array/text[] column with ["a,b"] produces {a,b}, which PostgREST parses as the two values a and b instead of the single value a,b. The same happens for elements containing {, }, ", \, surrounding whitespace, an empty string, or the literal NULL.

This is the array-literal counterpart of the in() filter escaping fixed in #1061.

Fix

Quote and backslash-escape each element that needs it, reusing the same escaping approach as the existing in() filter helper (added alongside it in Helpers):

public var rawValue: String {
  let elements = map { element -> String in
    let raw = element.rawValue
    if raw.hasPrefix("{"), raw.hasSuffix("}") {
      return raw
    }
    return escapePostgRESTArrayLiteralElement(raw)
  }
  return "{\(elements.joined(separator: ","))}"
}

Elements that are already safe (admin, 9:00, numbers) are emitted verbatim, so existing valid usage is unchanged.

Note on nested arrays

An element whose raw value both starts with { and ends with } is treated as an already-formed nested array literal and passed through unquoted, so arrays of arrays ([[1, 2], [3, 4]] -> {{1,2},{3,4}}) keep working. The trade-off is that a String element that is literally {...} will not be quoted — this is inherent to the string-based rawValue design, which can't distinguish a nested [Int] (whose rawValue is {1,2}) from the string "{1,2}". Elements with partial braces (e.g. a{b) are still quoted.

Testing

Added tests covering reserved characters (comma, brace), quote/backslash escaping, whitespace/empty/NULL, nested array literals, the AnyJSON.array path, and that safe/numeric values stay unquoted. They fail on main and pass with this change.

• swift test --filter PostgRESTTests — 105 passing (existing in() and snapshot tests unchanged)
• ./scripts/format.sh — clean