adapted esp-idf spiffs initialization

[OlliLenz]

Hi @matth-x,

If you use more than one spiffs partition in your project, it makes sense to adjust the .base_path of the partitions so that it is not just "/".
In the current version, however, this unfortunately leads to problems when using the esp-idf:

if you set the base_path to "/mo/", for example, you get an invalid argument error when initialising the spiffs partition, as the base path must not contain a slash at the end.
if you set the base_path to "/mo", the initialisation works, but the file names are no longer correct because they do not begin with a "/". An attempt is then made to save /mobootstats.jsn, for example, which does not work.
For this reason, a check has been introduced which, when setting the base_path, checks whether a "/" is present at the end of the define MOCPP_FILENAME_PREFIX. If this is the case, it is only removed for the base_path. Thus, the file names in the further course are also correct.

In addition, the define MOCPP_PARTITION_LABEL was introduced. The change from the former "ao" to "mo" could lead to problems in a production environment if devices are in circulation that have partitions with the name "ao", as these cannot or should not be changed OTA without further ado.

[matth-x]

Hi @OlliLenz, thanks for this contribution and getting more involved!

True, this is a severe defect. On the develop branch I already made a possible fix, but it doesn't allow "/" as the filename prefix, so still a drawback.

In the next few days I will merge the develop branch (and make this the v1.0 release finally), but likely will adopt a third approach of trimming the trailing / which is already used here to get the directory name from the filename prefix:

MicroOcpp/src/MicroOcpp/Core/FilesystemAdapter.cpp

Lines 298 to 308 in a532509

	char dname [MOCPP_MAX_PATH_SIZE];
	auto dlen = snprintf(dname, MOCPP_MAX_PATH_SIZE, "%s", MOCPP_FILENAME_PREFIX);
	if (dlen < 0 || dlen >= MOCPP_MAX_PATH_SIZE) {
	MOCPP_DBG_ERR("fn error: %i", dlen);
	return -1;
	}
	// trim trailing '/' if not root directory
	if (dlen >= 2 && dname[dlen - 1] == '/') {
	dname[dlen - 1] = '\0';
	}

The problem of strdup here is that it allocates a string on the heap which won't be released later. Anyway the SPIFFS integration becomes functional with this fix and the MOCPP_PARTITION_LABEL is a good idea. Thanks!