add a configuration file (#453)

* complete updated config package

* use envconfig+toml instead of viper. Add descriptions in example config file

* add unit tests

* debug gofmt on build server

* force dummy commit

* skip gofmt to validate other tests are passing

* unset env vars for example file parsing test

* cleanup tests

* test improvements

* re-enable gofmt

* naming

* PR comments

* fix failing test after olympus default endpoint change

* remove rdbms config

* set defaults in code

* add support for proxyfilteroff

* add basic auth params

* update gopkg.lock

* undo gopkg.lock changes made during merge

* remove defaults

* explicitly specify all env variables

* remove rdbms from example

* remove user and pass to disable basic auth by default

* switch to memory by default for the proxy

* fix tests after config file change

pkg/config/storage.go

@@ -0,0 +1,66 @@
+package config
+
+import validator "gopkg.in/go-playground/validator.v9"
+
+// StorageConfig provides configs for various storage backends
+type StorageConfig struct {
+	CDN   *CDNConfig   `validate:""`
+	Disk  *DiskConfig  `validate:""`
+	GCP   *GCPConfig   `validate:""`
+	Minio *MinioConfig `validate:""`
+	Mongo *MongoConfig `validate:""`
+}
+
+func setStorageTimeouts(s *StorageConfig, defaultTimeout int) {
+	if s == nil {
+		return
+	}
+	if s.CDN != nil && s.CDN.Timeout == 0 {
+		s.CDN.Timeout = defaultTimeout
+	}
+	if s.GCP != nil && s.GCP.Timeout == 0 {
+		s.GCP.Timeout = defaultTimeout
+	}
+	if s.Minio != nil && s.Minio.Timeout == 0 {
+		s.Minio.Timeout = defaultTimeout
+	}
+	if s.Mongo != nil && s.Mongo.Timeout == 0 {
+		s.Mongo.Timeout = defaultTimeout
+	}
+}
+
+// envconfig initializes *all* struct pointers, even if there are no corresponding defaults or env variables
+// deleteInvalidStorageConfigs prunes all such invalid configurations
+func deleteInvalidStorageConfigs(s *StorageConfig) {
+	validate := validator.New()
+
+	if s.CDN != nil {
+		if err := validate.Struct(s.CDN); err != nil {
+			s.CDN = nil
+		}
+	}
+
+	if s.Disk != nil {
+		if err := validate.Struct(s.Disk); err != nil {
+			s.Disk = nil
+		}
+	}
+
+	if s.GCP != nil {
+		if err := validate.Struct(s.GCP); err != nil {
+			s.GCP = nil
+		}
+	}
+
+	if s.Minio != nil {
+		if err := validate.Struct(s.Minio); err != nil {
+			s.Minio = nil
+		}
+	}
+
+	if s.Mongo != nil {
+		if err := validate.Struct(s.Mongo); err != nil {
+			s.Mongo = nil
+		}
+	}
+}