Updates instructions for self-managed connectors

[kosabogi]

Overview

This PR updates the Connector clients page in the Serverless documentation.

Related issue:

[Serverless]: Connector Run from source procedure clarifications #68

Preveiw

Connector clients

[elasticdocs]

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[leemthompo]

Thanks @kosabogi this is perfect! 👌

Just couple minor structural suggestions to improve the doc generally:

1. Add steps for the action sub-headings, I suggested Steps 1 and 2 but couldn't comment on the untouched sections below

• Step 3: Enter data source details in UI
• Step 4: Connect to an index

2. Swap the order of the Docker and source instructions to lead with Docker

[kosabogi]

Thanks @kosabogi this is perfect! 👌

Just couple minor structural suggestions to improve the doc generally:

1. Add steps for the action sub-headings, I suggested Steps 1 and 2 but couldn't comment on the untouched sections below

• Step 3: Enter data source details in UI
• Step 4: Connect to an index

2. Swap the order of the Docker and source instructions to lead with Docker

Thank you for your review @leemthompo ! I adjusted all of your suggestions in my newest commit.

Here are some details related the topics mentioned in the issue and my changes/findings related to them:

------------------------------- THE ISSUE AND THE RELATED CHANGES IN DETAILS -------------------------------

The values should match the literals in the UI and in the config.yml file:
Current text: Replace the values for host (your Elasticsearch endpoint), api_key, connector_id, and service_type.
Should be: Replace the values for elasticsearch.host (your Elasticsearch endpoint), elasticsearch.api_key, connector_id, and service_type. --- DONE

Should there be a link to the connectors report here or is clone command enough (I ask because the link to the example config.yml that is in the repo is linked...btw, I opened and copied it and then realized it was actually in the same repo...maybe say its actual name so I don't assume I'm getting it from somewhere else and I can easily find it in my cloned local directory) --- DONE, I decided to delete the link for the file on Github, and tell users that they can find the config.yml.example in the repo they've just cloned.

Further up. The API key instructions are out of date.
Current text: elasticsearch.api_key: Your Elasticsearch API key. You can create API keys under Security → API keys. Once you connector is running, you'll be able to create a new API key that is limited to only access the connector's index.
What needs to be updated: Security → API keys should be Management → Access → API keys --- DONE, but I didn't find this part to be true: Management → Access → API keys. It seems to be that it is Management → API keys. But I couldn't navigate there from the UI so I chose another simpler approach ("You can create a new API key by clicking on New in the API key section.")

The elasticsearch.host value is also on the new connector page. --- DONE

The editing of the config.yml is the same in both docker and python cases. The example was much more helpful in the docker section. We should probably reconcile them. --- DONE

Also are there special permissions required because my API key on the service returns 401 from the elasticsearch host. --- I couldn't find anything related to this, because I didn't receive error message related my API key.

[leemthompo]