Allow field names and map keys with dot (.)

[christophstrobl]

MongoDB 5 relaxed restrictions on special characters in field names as outlined in the reference documentation.

{
    "_id" : "id-1", 
    "key.with.dot" : "value", 
    "mapValue" : {
        "map.key.with.dot" : "mv"
    }
}

class WithMap {
    String id;
    @Field("key.with.dot")
    String value;
    Map<String, String> mapValue;
}

By default the mapping layer will able to read the above structure but reject map keys not having a mapKeyDotReplacement set on write. Users may use . as the replacement value to able to write map.key.with.dot from the above example. Still the dot notation within the value of an @Field annotation has a different semantic that would expand the parts of the field name into separate nested documents.

{
    "_id" : "id-1", 
    "key" : { "with" : { "dot" : "value" } },
    "mapValue" : {
        "map.key.with.dot" : "mv"
    }
}

One way of dealing with this issue could be to enhance the @Field annotation as follows:

public @interface Field {
    
    Class<? extends FieldNamingStrategy> fieldNaming() default FieldNamingStrategy.class;
    
    // ...
}

this would allow a certain level of flexibility eg. by providing predefined strategies for the above purpose as well as having a fixed value for meta annotation usage.