simplify/unify flags concatenation workflows

Implemented changes as suggested in #305 (closed)

• I have some problems figuring out the right way of squeezing flags as suggested in #305 (closed). I left a TODO note in the respective code line (funcs.resampling.concatFlags) and are requesting help from either one of you @palmb / @schaefed . (Or finlly a comprehensive documentation of the many pitfalls of history/flags object handling. I am really a bit lost any time i have to deal with those objects.)

saqc/funcs/resampling.py

@@ -486,7+486,7 @@
     target : str
         Field name of flags history to append to.
 
     method : {'inverse_fagg', 'inverse_bagg', 'inverse_nagg', 'inverse_fshift', 'inverse_bshift', 'inverse_nshift',
              'match'}, default 'match'
         The method used for projection of ``field`` flags onto ``target`` flags. See description above for more details.
 
@@ -559,7+559,7 @@
     history = flags.history[field].apply(dummy.index, func, func_kws)
     if squeeze:
         history = history.max()
-
-    flags.history[target].append(history)
+        meta = {
+            "func": f"concatFlags({field})",
+            "args": (field, target),
+            "kwargs": {
+                "method": method,
+                "freq": freq,
+                "drop": drop,
+                "squeeze": squeeze,
+                **kwargs,
+            },
+        }
+        flags.history[target].append(history, meta)
+    else:
+        flags.history[target].append(history)
 
     if drop:
         data, flags = tools.dropField(data=data, flags=flags, field=field)