GODRIVER-2800 Convert Session Interface to a Struct

[prestonvasquez]

GODRIVER-2800

Summary

Replace the session interface with a struct.

Background & Motivation

Currently there is only one implementation of the Session interface in the Go Driver, the sessionImpl struct. This is confusing to users since we export the Session interface but seal it from external use. Following best practices, we should investigating converting the session interface to a struct.

[mongodb-drivers-pr-bot]

API Change Report

./mongo

incompatible changes

##(Client).StartSession: changed from func(..../mongo/options.SessionOptions) (Session, error) to func(...*./mongo/options.SessionOptions) (*Session, error)
(*Client).UseSession: changed from func(context.Context, func(SessionContext) error) error to func(context.Context, func(context.Context) error) error
##(*Client).UseSessionWithOptions: changed from func(context.Context, *./mongo/options.SessionOptions, func(SessionContext) error) error to func(context.Context, *./mongo/options.SessionOptions, func(context.Context) error) error
NewSessionContext: changed from func(context.Context, Session) SessionContext to func(context.Context, Session) context.Context
##Session: changed from interface{AbortTransaction(context.Context) error; AdvanceClusterTime(./bson.Raw) error; AdvanceOperationTime(./bson.Timestamp) error; Client() Client; ClusterTime() ./bson.Raw; CommitTransaction(context.Context) error; EndSession(context.Context); ID() ./bson.Raw; OperationTime() ./bson.Timestamp; StartTransaction(..../mongo/options.TransactionOptions) error; WithTransaction(ctx context.Context, fn func(ctx SessionContext) (interface{}, error), opts ..../mongo/options.TransactionOptions) (interface{}, error); session()} to struct{clientSession *./x/mongo/driver/session.Client; client *Client; deployment ./x/mongo/driver.Deployment; didCommitAfterStart bool}
SessionContext: removed
SessionFromContext: changed from func(context.Context) Session to func(context.Context) *Session
WithSession: changed from func(context.Context, Session, func(SessionContext) error) error to func(context.Context, *Session, func(context.Context) error) error
XSession: removed

[matthewdale]

Looks good! 👍

Edit:
There are two undefined symbol compilation errors:

internal/integration/client_side_encryption_test.go:146:23: undefined: mongo.ContextWithSession
internal/integration/client_side_encryption_test.go:210:23: undefined: mongo.ContextWithSession

[matthewdale]

Looks good! 👍