feat(database): add agnostic engine

[jbrockopp]

Based off of #574, #663, #687, #692, #721, #722, #782, #810, #816 and #858

This change continues the refactor efforts initially introduced in the above PRs.

Those PRs ensured we leverage our DB library's (GORM) agnostic abstraction for integrating with a database.

Now, we can begin the efforts to create an agnostic engine that will be shared across all drivers:

server/database/database.go

Lines 49 to 66 in ab04f2f

	// engine represents the functionality that implements the Interface.
	engine struct {
	Config *Config
	Database *gorm.DB
	Logger *logrus.Entry
	build.BuildInterface
	hook.HookInterface
	log.LogInterface
	pipeline.PipelineInterface
	repo.RepoInterface
	schedule.ScheduleInterface
	secret.SecretInterface
	service.ServiceInterface
	step.StepInterface
	user.UserInterface
	worker.WorkerInterface
	}

We also add a Config{} that currently mirrors the Setup{} (I think "config" is a better name compared to "setup"):

server/database/database.go

Lines 29 to 47 in ab04f2f

	// Config represents the settings required to create the engine that implements the Interface.
	Config struct {
	// specifies the address to use for the database engine
	Address string
	// specifies the level of compression to use for the database engine
	CompressionLevel int
	// specifies the maximum idle connections for the database engine
	ConnectionIdle int
	// specifies the connection duration to use for the database engine
	ConnectionLife time.Duration
	// specifies the maximum open connections for the database engine
	ConnectionOpen int
	// specifies the driver to use for the database engine
	Driver string
	// specifies the encryption key to use for the database engine
	EncryptionKey string
	// specifies to skip creating tables and indexes for the database engine
	SkipCreation bool
	}

This will help ensure we reduce the amount of duplicate code across the currently supported drivers:

• postgres
• sqlite

Also, this will lower the barrier to entry for adding support for future drivers assuming they are supported by GORM.

Basically, we're ensuring we leverage the full functionality our DB library (GORM) has to offer.

[codecov]

Codecov Report

Merging #868 (ab04f2f) into main (a5fc7c6) will increase coverage by 0.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #868      +/-   ##
==========================================
+ Coverage   71.92%   72.04%   +0.12%     
==========================================
  Files         307      310       +3     
  Lines       12872    12930      +58     
==========================================
+ Hits         9258     9316      +58     
  Misses       3168     3168              
  Partials      446      446              

Impacted Files	Coverage Δ
database/database.go	100.00% <ø> (ø)
database/close.go	100.00% <100.00%> (ø)
database/driver.go	100.00% <100.00%> (ø)
database/validate.go	100.00% <100.00%> (ø)