[TECHDEBT] Consolidated PostgresContext and PostgresDB (#149)

[Olshansk]

Description

Tend to tech debt in the persistence module related to simplifying the PostgresContext struct.

Issue

Fixes #149

Type of change

Please mark the relevant option(s):

• New feature, functionality or library
• Bug fix (non-breaking change which fixes an issue)
• Code health or cleanup
• Major breaking change
• Documentation
• Other: <REPLACE_ME>

List of changes

• Consolidates PostgresContext and PostgresDB
• Reduces scope of Tx and BlockStore
• Improve error handling in NewFuzzTestPostgresContext

Testing

• make test_all
• LocalNet w/ all of the steps outlined in the README

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have tested my changes using the available tooling
• If applicable, I have made corresponding changes to related local or global README
• If applicable, I have added new diagrams using mermaid.js
• If applicable, I have added tests that prove my fix is effective or that my feature works

[andrewnguyen22]

You didn't complete the original ask about consolidating txn and tx.

Let me add more detail:

type PostgresContext struct {
	Height     int64 // TODO(olshansky): `Height` is only externalized for testing purposes. Replace with helpers...
	conn       *pgx.Conn
	tx         pgx.Tx                          // This field is `tx`
	blockstore kvstore.KVStore
}

// These functions use Txn() 

func (pg *PostgresContext) GetCtxAndTxn() (context.Context, pgx.Tx, error) {
	return context.TODO(), pg.GetTxn(), nil
}

func (pg *PostgresContext) GetTxn() pgx.Tx {
	return pg.tx
}

Let's consolidate this terminology in order to lower cognitive load and increase readability

Also, please ensure that the structure field uses the GetTxn() function instead of accessing the private field directly:

Ex.

if err := p.tx.Rollback(ctx); err != nil {
		return err
	}

[Olshansk]

Got it now, ty! I def like this better.

Also, pro tip for markdown. You can add syntax highlighting by specifying the language after the triple backtick:

[andrewnguyen22]

Please change this PR description to fill out the template provided

I don't believe it's as clear to the outsider.

Also, consider adding more detail to the changelog for tracking purposes

[andrewnguyen22]

Why is this commented out?

Also, if you're going to touch this code, it seems like you could easily satisfy that TODO there.

Perhaps it's out of scope?

[Olshansk]

It was mainly to tend to require.NotContains(t, newActor.StakedTokens, "invalid") given the require.NotContains requirment above.

You're correct that it's out-of-scope so I reverted the changes and updated the comment

[andrewnguyen22]

I don't want to see txn anywhere in this code anymore. Let's keep it consistent

Examples:

ctx, txn, err := p.GetCtxAndTx()

func (p *PostgresContext) GetChainsForActor(
	ctx context.Context,
	txn pgx.Tx,

[Olshansk]

I like it! Done

[andrewnguyen22]

Resolve conflicts then approve incoming!

[Olshansk]

@andrewnguyen22 Merged with main and pushed.