Stop putting email-to URI bit into option field of spectrum URI.

Added note about how it we shouldn't have ever been doing this.

InterSpec/QRSpectrum.h

@@ -141,6 +141,10 @@ enum EncodeOptions
    For example, a returned URI will start with:
    "mailto:user@example.com?subject=spectrum&body=Spectrum%20URI%0D%0Araddata:..."
    and it will not be strictly URL encoded.
+   
+   Note that this option will not be written/indicated in the URI; however, this value 0x20, was being written
+   until 20231202, so we will ignore this bit when it is in URIs, for the time being, and in the future if more
+   options are added, consider skipping this bit.
    */
   AsMailToUri = 0x20,
 };//enum EncodeOptions

src/QRSpectrum.cpp

@@ -1473,7 +1473,13 @@ vector<string> url_encode_spectrum( const UrlSpectrum &m,
 
   cout << "--------------------------------------------------------------------------------\n";
   cout << "URL start:\n\t";
-  const string url_start = string("RADDATA://G0/") + sm_hex_digits[encode_options & 0x0F];
+
+  const uint8_t used_options = (encode_options & (~EncodeOptions::AsMailToUri));
+  const char more_sig_char = sm_hex_digits[(used_options >> 4) & 0x0F];
+  const char less_sig_char = sm_hex_digits[used_options & 0x0F];
+  const string opt_str = ((more_sig_char == '0') ? string() : (string() + more_sig_char)) + less_sig_char;
+
+  const string url_start = "RADDATA://G0/" + opt_str;
   cout << "\t" << url_start << endl;
   cout << "--------------------------------------------------------------------------------\n";
 
@@ -1665,9 +1671,11 @@ std::vector<UrlEncodedSpec> url_encode_spectra( const std::vector<UrlSpectrum> &
   if( measurements.size() > 9 )
     throw runtime_error( "url_encode_spectra: to many measurements passed in." );
 
-
-  if( encode_options & ~(EncodeOptions::NoDeflate | EncodeOptions::NoBaseXEncoding | EncodeOptions::CsvChannelData
-                         | EncodeOptions::NoZeroCompressCounts | EncodeOptions::UseUrlSafeBase64 | EncodeOptions::AsMailToUri) )
+  const uint8_t allowed_bits = (EncodeOptions::NoDeflate | EncodeOptions::NoBaseXEncoding
+                                | EncodeOptions::CsvChannelData | EncodeOptions::NoZeroCompressCounts
+                                | EncodeOptions::UseUrlSafeBase64 | EncodeOptions::AsMailToUri);
+  const uint8_t not_allowed_bits = ~allowed_bits;
+  if( encode_options & not_allowed_bits )
     throw runtime_error( "url_encode_spectra: invalid option passed in - see EncodeOptions." );
 
   assert( encode_options < 0x80 );
@@ -1717,8 +1725,9 @@ std::vector<UrlEncodedSpec> url_encode_spectra( const std::vector<UrlSpectrum> &
       url_start = string("RADDATA://G0/");
     }
 
-    const char more_sig_char = sm_hex_digits[(encode_options >> 4) & 0x0F];
-    const char less_sig_char = sm_hex_digits[encode_options & 0x0F];
+    const uint8_t used_options = (encode_options & (~EncodeOptions::AsMailToUri));
+    const char more_sig_char = sm_hex_digits[(used_options >> 4) & 0x0F];
+    const char less_sig_char = sm_hex_digits[used_options & 0x0F];
 
     url_start += ((more_sig_char == '0') ? string() : (string() + more_sig_char))
                  + (string() + less_sig_char)
@@ -2019,6 +2028,8 @@ EncodedSpectraInfo get_spectrum_url_info( std::string url )
       answer.m_encode_options = hex_to_dec( url[0] );
     }
 
+    // Note that `EncodeOptions::AsMailToUri = 0x20` was written previous to 20231202, even though it
+    //  shouldnt have been - so we will ignore this bit
     const uint8_t allowed_bits = (EncodeOptions::NoDeflate | EncodeOptions::NoBaseXEncoding
                                   | EncodeOptions::CsvChannelData | EncodeOptions::NoZeroCompressCounts
                                   | EncodeOptions::UseUrlSafeBase64 | EncodeOptions::AsMailToUri);