Handle symbol param keys during filtering

In testing these keys can be symbols, so when we're working with
encodings make sure we have strings before trying to force any encodings
on keys.

lib/grape_logging/loggers/filter_parameters.rb

@@ -37,14 +37,16 @@ def clean_parameters(parameters)
 
       def build_encoding_map(parameters)
         parameters.each_with_object({}) do |(k, v), h|
-          h[k.dup.force_encoding(Encoding::ASCII_8BIT)] = [k.encoding, v.is_a?(Hash) ? build_encoding_map(v) : nil]
+          key_str = k.to_s
+          h[key_str.dup.force_encoding(Encoding::ASCII_8BIT)] = [key_str.encoding, v.is_a?(Hash) ? build_encoding_map(v) : nil]
         end
       end
 
       def transform_key_encoding(parameters, encoding_map)
         parameters.each_with_object({}) do |(k, v), h|
-          encoding, children_encoding_map = encoding_map[k]
-          h[k.dup.force_encoding(encoding)] = v.is_a?(Hash) ? transform_key_encoding(v, children_encoding_map) : v
+          key_str = k.to_s
+          encoding, children_encoding_map = encoding_map[key_str]
+          h[key_str.dup.force_encoding(encoding)] = v.is_a?(Hash) ? transform_key_encoding(v, children_encoding_map) : v
         end
       end
     end

spec/lib/grape_logging/loggers/filter_parameters_spec.rb

@@ -78,4 +78,14 @@
     let(:replacement) { 'CUSTOM_REPLACEMENT' }
     it_behaves_like 'filtering'
   end
+
+  context 'with symbol keys, which occur during automated testing' do
+    let(:mock_request) { OpenStruct.new(params: { sneaky_symbol: 'hey!' }) }
+
+    it 'converts keys to strings' do
+      expect(subject.parameters(mock_request, nil)).to eq(params: {
+        'sneaky_symbol' => 'hey!',
+      })
+    end
+  end
 end