Summary

Mongo driver is incorrectly resolving the key/value pairs of authMechanismProperties in a SRV connection string. 

Driver version: 3.1.0

Mongo server version: v8

Topology: Standalone cloud cluster

How to Reproduce

public static void Process()
{
    var text = "mongodb+srv://<cluseter>/?retryWrites=true&w=1&maxPoolSize=100&authMechanism=MONGODB-OIDC&authSource=%24external&authMechanismProperties=ENVIRONMENT:azure,prop1:user,prop2:userType";
    var mongoConnection = MongoClientSettings.FromConnectionString(text);
    Console.WriteLine(mongoConnection.Credential.GetMechanismProperty<string>("ENVIRONMENT", ""));
// Prints "azure,prop1:user,prop2:userType" instead of just "azure"
} 

Additional Background

Noticed this is happening because of the line of code https://github.com/mongodb/mongo-csharp-driver/blob/660f33d01fe9604044e2877e4564ce10dbfc2593/src/MongoDB.Driver/Core/Configuration/ConnectionString.cs#L909, which doesn't unescape the authMechanismProperties value(it contains the encoded values for all special characters and doesn't work well with the split happening in GetAuthMechanismProperties method) while building a resolved SRV connection string