Add examples of how to use operators/decorators in docstrings

[tatiana]

Context

In the past, we had a tutorial which illustrated how to use each of our operators/decorators: https://github.com/astronomer/astro-sdk/blob/be6280df00ccff0d7a1c0dfb099b2065303dbe88/REFERENCE.md

Since we started auto-generating the documentation with Sphinx, the overall description of each operator is incomplete:

Depends on:

• [x] #586
• [x] #587
• [x] #588
• [ ] #589
• [x] #590
• [x] #591
• [x] #592
• [ ] #593
• [x] #594

Acceptance criteria

Have a reference page per operator/decorator similar to https://airflow.apache.org/docs/apache-airflow-providers-amazon/stable/operators/ecs.html#howto-operator-ecsoperator

In which we reference parts of an (automated tested) example DAG which illustrates the usage of that operator/decorator.

Many of these use cases already exist in our example DAGs - we should reference them.

• [X] load_file, including examples - story points: 5
  • (HTTP + CSV) loading to a table
  • load to dataframe
  • native load with BQ
  • native load with Snowflake
  • native load with fallback
  • non-native support
  • specifying the schema (tables.columns)
• [x] transform - story points: 2
  • arguments are tables, illustrating templating
  • one argument is a dataframe
• [X] drop_table - story points: 1
  • single example
• [ ] run_raw_sql - story points: 2
  • without handler function
  • with handler function
• [X] append - story points: 1
  • single example
• [ ] merge - story points: 2
  • with conflicts (what options the user has)
  • without conflicts
• [x] export_file - story points: 2
  • exporting from a table
  • exporting from a dataframe
• [ ] dataframe - story points: 1
  • single example
• [X] cleanup - story points: 1
  • single example

If no example DAGs or operators are illustrating the functionalities, we should create them.

[utkarsharma2]

@tatiana can we add story points to it?

[kaxil]

@utkarsharma2 This one is an "epic" that encompasses several docs issues as listed in the PR description so we don't need to add story points to this task

[utkarsharma2]

All of the subtasks have been completed. Closing this issue.