Fix cluster_id length check in startup.py

[MKoesters]

MAX_ID_LENGTH suggests a maximum length, not a static length. I adapted the condition accordingly

[XaverStiensmeier]

Good catch. At the beginning I planned to set it only as a maximum. Later I thought that it might be wise to not allow shorter cluster ids to make it less likely to have two clusters with the same id. However, this is not a fix. A fix is to perform a bibigrid.core.utility.id_generation.is_unique_cluster_id check on the given cluster id to guarantee that the id is not in use before creation, which is much safer.

changing != to > also has to be done for rest_startup.

[MKoesters]

Good catch. At the beginning I planned to set it only as a maximum. Later I thought that it might be wise to not allow shorter cluster ids to make it less likely to have two clusters with the same id. However, this is not a fix. A fix is to perform a bibigrid.core.utility.id_generation.is_unique_cluster_id check on the given cluster id to guarantee that the id is not in use before creation, which is much safer.

changing != to > also has to be done for rest_startup.

I'll have a look at this