Jetty HttpClient implementation of TelegramClient

[valkuc]

Hi.
In my project I'm using Jetty Server. I came to the conclusion that additional dependencies on OkHttp client and Kotlin - is too much. So I decided to create TelegramClient implementation that uses Jetty HttpClient instead of OkHttp.

To use it, just include

<dependency>
    <groupId>org.telegram</groupId>
    <artifactId>telegrambots-client-jetty-adapter</artifactId>
</dependency>

instead of

<dependency>
    <groupId>org.telegram</groupId>
    <artifactId>telegrambots-client</artifactId>
</dependency>

Some considerations:

1. It would be nice to move OkHttp from telegrambots-client to separate dependency, for example telegrambots-client-okhttp-adapter.
2. Move common client parts (like creation of request body) to abstract class.

[valkuc]

@rubenlagus Hi. Any troubles with merging?

[rubenlagus]

Hi @valkuc , no concerns but can you add one lesson for this client as well here: https://github.com/rubenlagus/TelegramBotsDocumentation

[valkuc]

Hi @valkuc , no concerns but can you add one lesson for this client as well here: https://github.com/rubenlagus/TelegramBotsDocumentation

Hi. Yep, will do.

[Chase22]

Move common client parts (like creation of request body) to abstract class.

I did actually consider this when making the telegram client, unfortunately there's no unified interface for multipart requests. It's something we'd have to implement ourselves

[valkuc]

Hi @valkuc , no concerns but can you add one lesson for this client as well here: https://github.com/rubenlagus/TelegramBotsDocumentation

Hi. Yep, will do.

@rubenlagus maybe I'm blind but I don't see my changes in master. Looks like something goes wrong with merge.

[rubenlagus]

Hi @valkuc , no concerns but can you add one lesson for this client as well here: https://github.com/rubenlagus/TelegramBotsDocumentation

Hi. Yep, will do.

@rubenlagus maybe I'm blind but I don't see my changes in master. Looks like something goes wrong with merge.

I'll merge it when I have a bit of time, there are some extra fields that need to be added to the media classes