Handle pagination

The spec on this is pretty subpar. This is hacked in to resolve a
production issue!  Failed to realize that the Ruby SDK limits parameter
responses to 10 because the CLI does not.

lib/psenv/retriever.rb

@@ -38,9 +38,16 @@ module Psenv
     end
 
     def parameters
-      ssm.
-        get_parameters_by_path(path: @path, with_decryption: true).
-        parameters
+      parameters = []
+      response = ssm.get_parameters_by_path(path: @path, with_decryption: true)
+      parameters << response.parameters
+
+      while response.next_page?
+        response = response.next_page
+        parameters << response.parameters
+      end
+
+      parameters.flatten
     rescue StandardError => error
       raise RetrieveError, error
     end

spec/retriever_spec.rb

@@ -41,7 +41,7 @@ RSpec.describe Psenv::Retriever do
 
     subject { Psenv::Retriever.new("/psenv/test").call }
 
-    context "with a successful request" do
+    context "with a single page request" do
       before(:each) do
         allow(ssm).to receive(:get_parameters_by_path) {
           OpenStruct.new(
@@ -60,6 +60,34 @@ RSpec.describe Psenv::Retriever do
       end
     end
 
+    context "with multiple pages" do
+      before(:each) do
+        allow(ssm).to receive(:get_parameters_by_path) {
+          OpenStruct.new(
+            parameters: [{
+              name: "/psenv/test/API_KEY",
+              value: "value",
+              type: "String",
+              version: 1,
+            }],
+            next_page?: true,
+            next_page: OpenStruct.new(
+              parameters: [{
+                name: "/psenv/test/CLIENT_KEY",
+                value: "value",
+                type: "String",
+                version: 1,
+              }],
+            ),
+          )
+        }
+      end
+
+      it "returns both parameters" do
+        expect(subject).to eq("API_KEY" => "value", "CLIENT_KEY" => "value")
+      end
+    end
+
     context "when the request fails" do
       before(:each) { allow(ssm).to receive(:get_parameters_by_path).and_raise }