Fix bytea[] query params

Since arrays are text-encoded, we need to text-encode them inside
arrays.

spec/pq/param_spec.cr

@@ -16,6 +16,7 @@ describe PQ::Param do
       it_encodes_array([1, 2, 3], "{1,2,3}")
       it_encodes_array([1.2, 3.4, 5.6], "{1.2,3.4,5.6}")
       it_encodes_array([%(a), %(\\b~), %(c\\"d), %(\uFF8F)], %({"a","\\\\b~","c\\\\\\"d","\uFF8F"}))
+      it_encodes_array([%(this is a "slice").to_slice], %({"\\\\x7468697320697320612022736c69636522"}))
       it_encodes_array(["baz, bar"], %({"baz, bar"}))
       it_encodes_array(["foo}"], %({"foo}"}))
       it_encodes_array([nil, nil], %({NULL,NULL}))

src/pq/param.cr

@@ -121,8 +121,10 @@ module PQ
     end
 
     def self.encode_array(io, value : Bytes)
-      io << '"'
-      io << String.new(value).gsub(%("), %(\\"))
+      io << %{"\\\\x}
+      value.each do |byte|
+        byte.to_s io, base: 16, precision: 2
+      end
       io << '"'
     end