Improve parameter parsing (#583)

* DigiKey: Skip empty values

* Move improved range detection from LCSCProvider to ParameterDTO class
Improve numeric value detection by moving extra info to value_text

* ParameterDTO: Add micro unit prefix

* Bring $value_text2 to a defined state

* ParameterDTO: Don't overwrite $unit if it's not empty

* ParameterDTO: Don't overwrite $unit if it's not empty

* Correct some inaccuacies in comments

* Added tests and fixed certain edge cases in parsing parameters

* Added more tests for parameter parsing

---------

Co-authored-by: Jan Böhmer <mail@jan-boehmer.de>

src/Services/InfoProviderSystem/Providers/DigikeyProvider.php

@@ -210,6 +210,10 @@ class DigikeyProvider implements InfoProviderInterface
                 $footprint_name = $parameter['Value'];
             }
 
+            if (in_array(trim($parameter['Value']), array('', '-'), true)) {
+                continue;
+            }
+
             $results[] = ParameterDTO::parseValueIncludingUnit($parameter['Parameter'], $parameter['Value']);
         }
 
@@ -265,4 +269,4 @@ class DigikeyProvider implements InfoProviderInterface
         ];
     }
 
-}
+}