refactor: consolidate property fetching for nginx plugin into golang codebase

Also update the documentation to include docs for all properties.

tests/unit/nginx-vhosts_8.bats

@@ -20,6 +20,26 @@ teardown() {
   echo "status: $status"
   assert_success
 
+  run /bin/bash -c "dokku nginx:show-config $TEST_APP"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "client_max_body_size 1m;"
+
+  run /bin/bash -c "dokku nginx:set $TEST_APP client-max-body-size 2m"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku proxy:build-config $TEST_APP"
+  echo "output: $output"
+  echo "status: $status"
+  assert_success
+
+  run /bin/bash -c "dokku nginx:show-config $TEST_APP"
+  echo "output: $output"
+  echo "status: $status"
+  assert_output_contains "client_max_body_size 2m;"
+
   run /bin/bash -c "dokku nginx:set $TEST_APP client-max-body-size"
   echo "output: $output"
   echo "status: $status"
@@ -33,22 +53,7 @@ teardown() {
   run /bin/bash -c "dokku nginx:show-config $TEST_APP"
   echo "output: $output"
   echo "status: $status"
-  assert_output_contains "client_max_body_size" 0
-
-  run /bin/bash -c "dokku nginx:set $TEST_APP client-max-body-size 1m"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-
-  run /bin/bash -c "dokku proxy:build-config $TEST_APP"
-  echo "output: $output"
-  echo "status: $status"
-  assert_success
-
-  run /bin/bash -c "dokku nginx:show-config $TEST_APP"
-  echo "output: $output"
-  echo "status: $status"
-  assert_output_contains "client_max_body_size 1m;" 1
+  assert_output_contains "client_max_body_size 1m;"
 }
 
 @test "(nginx-vhosts) nginx:set proxy-read-timeout" {