Implement Lame Duck Mode Event Handler

[pzajaczkowski]

Resolves #23

I had two ideas for approaching this issue:

• Make WritableServerInfo property and add setter, that will check if LDM has changed to true
• Add a trigger method that writes the event to a channel in NatsConnection and invoke it directly from NatsReadProtocolProcessor after recieving INFO from server with LDM.

I decided to go with first option.

There is one thing i am not sure of: should anything be passed as argument to the LameDuckModeActivated event? Currently, it is an empty string.

[mtmk]

@pzajaczkowski thanks for the PR. long overdue that issue ;)

• Make WritableServerInfo property and add setter, that will check if LDM has changed to true
• Add a trigger method that writes the event to a channel in NatsConnection and invoke it directly from NatsReadProtocolProcessor after recieving INFO from server with LDM.

I decided to go with first option.

I think that's fine.

There is one thing i am not sure of: should anything be passed as argument to the LameDuckModeActivated event? Currently, it is an empty string.

Potentially passing the host might be a interesting. Or a copy of the server info?

EDIT: What do you think about passing Uri of the host similar to the proposal in PR #712

[mtmk]

LGTM thanks @pzajaczkowski