Wekan: upgrade from 7.49 to 7.51 failed with mongod error

Hi,

# mongod --version                                                                                                                                                      
db version v6.0.15                                                                                                                                                                            
Build Info: {                                                                                                                                                                                 
    "version": "6.0.15",                                                                                                                                                                      
    "gitVersion": "7494119c41ca4e13b493e9f048df4032164e860e",                                                                                                                                 
    "openSSLVersion": "OpenSSL 1.1.1w  11 Sep 2023",                                                                                                                                          
    "modules": [],                                                                                                                                                                            
    "allocator": "tcmalloc",                                                                                                                                                                  
    "environment": {                                                                                                                                                                          
        "distmod": "debian11",                                                                                                                                                                
        "distarch": "x86_64",                                                                                                                                                                 
        "target_arch": "x86_64"                                                                                                                                                               
    }                                                                                                                                                                                         
}                                                                                                                                                                                             
# tail -n 50 /var/log/mongodb/mongod.log                                                                                                                                
{"t":{"$date":"2024-07-29T08:42:14.738+02:00"},"s":"I",  "c":"STORAGE",  "id":22297,   "ctx":"initandlisten","msg":"Using the XFS filesystem is strongly recommended with the WiredTiger stora
ge engine. See http://dochub.mongodb.org/core/prodnotes-filesystem","tags":["startupWarnings"]}                                                                                               
{"t":{"$date":"2024-07-29T08:42:14.807+02:00"},"s":"I",  "c":"STORAGE",  "id":22315,   "ctx":"initandlisten","msg":"Opening WiredTiger","attr":{"config":"create,cache_size=7444M,session_max=
33000,eviction=(threads_min=4,threads_max=4),config_base=false,statistics=(fast),log=(enabled=true,remove=true,path=journal,compressor=snappy),builtin_extension_config=(zstd=(compression_lev
el=6)),file_manager=(close_idle_time=600,close_scan_interval=10,close_handle_minimum=2000),statistics_log=(wait=0),json_output=(error,message),verbose=[recovery_progress:1,checkpoint_progres
s:1,compact_progress:1,backup:0,checkpoint:0,compact:0,evict:0,history_store:0,recovery:0,rts:0,salvage:0,tiered:0,timestamp:0,transaction:0,verify:0,log:0],"}}                              
{"t":{"$date":"2024-07-29T08:42:16.836+02:00"},"s":"I",  "c":"STORAGE",  "id":4795906, "ctx":"initandlisten","msg":"WiredTiger opened","attr":{"durationMillis":2029}}                        
{"t":{"$date":"2024-07-29T08:42:16.836+02:00"},"s":"I",  "c":"RECOVERY", "id":23987,   "ctx":"initandlisten","msg":"WiredTiger recoveryTimestamp","attr":{"recoveryTimestamp":{"$timestamp":{"
t":0,"i":0}}}}                                                                                                                                                                                
{"t":{"$date":"2024-07-29T08:42:17.249+02:00"},"s":"W",  "c":"CONTROL",  "id":22120,   "ctx":"initandlisten","msg":"Access control is not enabled for the database. Read and write access to d
ata and configuration is unrestricted","tags":["startupWarnings"]}                                                                                                                            
{"t":{"$date":"2024-07-29T08:42:17.249+02:00"},"s":"W",  "c":"CONTROL",  "id":22178,   "ctx":"initandlisten","msg":"/sys/kernel/mm/transparent_hugepage/enabled is 'always'. We suggest settin
g it to 'never' in this binary version","tags":["startupWarnings"]}                                                                                                                           
{"t":{"$date":"2024-07-29T08:42:17.249+02:00"},"s":"W",  "c":"CONTROL",  "id":5123300, "ctx":"initandlisten","msg":"vm.max_map_count is too low","attr":{"currentValue":65530,"recommendedMini
mum":102400,"maxConns":51200},"tags":["startupWarnings"]}                                                                                                                                     
{"t":{"$date":"2024-07-29T08:42:17.501+02:00"},"s":"F",  "c":"CONTROL",  "id":20573,   "ctx":"initandlisten","msg":"Wrong mongod version","attr":{"error":"UPGRADE PROBLEM: Found an invalid f
eatureCompatibilityVersion document (ERROR: Location4926900: Invalid featureCompatibilityVersion document in admin.system.version: { _id: \"featureCompatibilityVersion\", version: \"4.4\" }.
 See https://docs.mongodb.com/master/release-notes/5.0-compatibility/#feature-compatibility. :: caused by :: Invalid feature compatibility version value, expected '5.0' or '5.3' or '6.0. See
 https://docs.mongodb.com/master/release-notes/5.0-compatibility/#feature-compatibility.). If the current featureCompatibilityVersion is below 5.0, see the documentation on upgrading at http
s://docs.mongodb.com/master/release-notes/5.0/#upgrade-procedures."}}                                                                                                                         

So I indeed get a compatibility problem.