Use variables instead of constants in dev seeds

While running the `dev_seed` twice, as we do in the tests, we were
getting the following warnings:

```
db/dev_seeds/proposals.rb:1: warning: already initialized constant
IMAGE_FILES

db/dev_seeds/budgets.rb:1: warning: already initialized constant
INVESTMENT_IMAGE_FILES
```

So we're extracting a method which allows us to use local variables
while removing duplication.

We had this warning with every version of Ruby, not just Ruby 2.7, but
since we're getting rid of all the warnings, we're taking care of this
one as well.

db/dev_seeds.rb

@@ -36,6 +36,17 @@ def random_locales_attributes(**attribute_names_with_values)
   end
 end
 
+def add_image_to(imageable, sample_image_files)
+  # imageable should respond to #title & #author
+  imageable.image = Image.create!({
+    imageable: imageable,
+    title: imageable.title,
+    attachment: Rack::Test::UploadedFile.new(sample_image_files.sample),
+    user: imageable.author
+  })
+  imageable.save!
+end
+
 log "Creating dev seeds for tenant #{Tenant.current_schema}" unless Tenant.default?
 
 load_dev_seeds "settings"

db/dev_seeds/budgets.rb

@@ -1,4 +1,5 @@
-INVESTMENT_IMAGE_FILES = %w[
+def add_image_to_investment(investment)
+  image_files = %w[
     brennan-ehrhardt-25066-unsplash_713x513.jpg
     carl-nenzen-loven-381554-unsplash_713x475.jpg
     carlos-zurita-215387-unsplash_713x475.jpg
@@ -13,15 +14,7 @@ INVESTMENT_IMAGE_FILES = %w[
                     "investments", filename)
   end
 
-def add_image_to(imageable)
-  # imageable should respond to #title & #author
-  imageable.image = Image.create!({
-    imageable: imageable,
-    title: imageable.title,
-    attachment: Rack::Test::UploadedFile.new(INVESTMENT_IMAGE_FILES.sample),
-    user: imageable.author
-  })
-  imageable.save!
+  add_image_to(investment, image_files)
 end
 
 section "Creating Budgets" do
@@ -122,7 +115,7 @@ section "Creating Investments" do
       terms_of_service: "1"
     }.merge(translation_attributes))
 
-    add_image_to(investment) if Random.rand > 0.5
+    add_image_to_investment(investment) if Random.rand > 0.5
   end
 end
 
@@ -167,7 +160,7 @@ section "Winner Investments" do
       price: rand(10000..heading.price),
       terms_of_service: "1"
     )
-    add_image_to(investment) if Random.rand > 0.3
+    add_image_to_investment(investment) if Random.rand > 0.3
   end
   budget.headings.each do |heading|
     Budget::Result.new(budget, heading).calculate_winners

db/dev_seeds/proposals.rb

@@ -1,4 +1,5 @@
-IMAGE_FILES = %w[
+def add_image_to_proposal(proposal)
+  image_files = %w[
     firdouss-ross-414668-unsplash_846x475.jpg
     nathan-dumlao-496190-unsplash_713x475.jpg
     steve-harvey-597760-unsplash_713x475.jpg
@@ -10,15 +11,7 @@ IMAGE_FILES = %w[
                     "proposals", filename)
   end
 
-def add_image_to(imageable)
-  # imageable should respond to #title & #author
-  imageable.image = Image.create!({
-    imageable: imageable,
-    title: imageable.title,
-    attachment: Rack::Test::UploadedFile.new(IMAGE_FILES.sample),
-    user: imageable.author
-  })
-  imageable.save!
+  add_image_to(proposal, image_files)
 end
 
 section "Creating Proposals" do
@@ -47,7 +40,7 @@ section "Creating Proposals" do
         proposal.save!
       end
     end
-    add_image_to proposal
+    add_image_to_proposal proposal
   end
 end
 
@@ -75,7 +68,7 @@ section "Creating Archived Proposals" do
         proposal.save!
       end
     end
-    add_image_to proposal
+    add_image_to_proposal proposal
   end
 end
 
@@ -103,7 +96,7 @@ section "Creating Successful Proposals" do
         proposal.save!
       end
     end
-    add_image_to proposal
+    add_image_to_proposal proposal
   end
 
   tags = Tag.where(kind: "category")
@@ -128,7 +121,7 @@ section "Creating Successful Proposals" do
         proposal.save!
       end
     end
-    add_image_to proposal
+    add_image_to_proposal proposal
   end
 end